Sure, at some level the technology will come in to play but nobody will 'start a high tech bank'. For instance, ING direct (one of the efforts of the banking industry to leverage the use of technology) was jump started from the legacy ING systems and as far as I know still ties in to them for all of their back-end stuff.
When I was the 'systems administrator' for the corporate division of a bank (in 1986 or so) we had daily rounds of getting the signatures of the various people responsible that the totals for the night batch runs were correct. That's the sort of responsibility you're talking about, I can't imagine that an MD5 or some digital signature would be sufficient today, it's all about procedures and accountability, emphatically not about technology.
I got one of the first PCs the bank bought on account of our project manager being very forward thinking but nobody ever thought of it as more than a curiosity and something that might be a handy replacement for the terminals.
That attitude has changed a bit but not by much and that's 25 years.
I currently work in a fairly large financial institution, giving them a web presence for various services and the backend system is no longer a mainframe but an AS/400. Though it still runs COBOL-based apps, so it's really no different than the standard mainframe.
Google built another search engine, which ran on a cluster of PCs and did so more efficiently than the big competitor at the time, AltaVista, which ran (afaik) on a cluster of Dec Alphas. Because google needed lot of horsepower and had a tight budget they came up with some pretty clever packaging ideas for their cluster.
In that sense both these companies took the best route to a solution. Now a search engine is materially different from a bank in that if something goes wrong in a bank the potential damage (not just to the bank, but also to the customers of the bank) is enormous.
A search engine that spits out 'wrong' results is still a search engine. A bank that doesn't know where your money went is no longer a bank (at least, not for very long).
Financial institutions rely heavily on their image of reliability, much more so than any web company.
In this case, I'm referring to banking. You've got an industry that is based almost entirely on legacy systems that has not evolved with the progress of technology. As correctly pointed out, you would not want to modify an existing legacy system to move it to a new technology, which is why nobody has done so. What I'm referring to is a new, from scratch, bank with new technology. One that would allow you to disconnect from the current banking model and allow you to offer services that nobody could provide with today's legacy systems.
This combined with the fact that if you ask any bank customer they will tell you how much they hate their bank and hate the service. Sounds like it's ripe for the pickings with the right investment, investors and people.
As for the banking bit. You are missing my point, nobody builds a bank because of the technology, people found new banks because of the money. If that means adapting old, tried and true technology to jump trough new hoops then that's a cost of business. Bankers are conservative by nature, not because they like it but because it makes very good business sense when you're a bank. It's no coincidence that banks, insurance companies and governments are the areas where the mainframe is still dominant.
I'm really not sure what kind of services you could offer with a 'new' software stack that you could not offer with the old one. Bank transfers are routinely done in seconds between banks, you can pay with everything from credit cards to mobile phones and computers, they seem to have done a remarkable job at adapting to new tech while remaining conservative at heart.
People hate their banks mostly for the costs and for the lack of human interest, rarely if ever because of the lack of technology. In fact, I could do with less technology and better human interaction.
I think the best part would be that because of the legacy technology in place at existing banks, they would have a very hard time making changes to adapt to anything new that would be offered. Just imagine adding a new account type that isn't checking or savings and has new rules. How long would it take for a bank to re-write their backend system to incorporate that change? A long time.
If a disruptor entered banking and did offer this kind of change, I think you'd have banks banging down your door to buy you out, if nothing else.
There is a big temptation to assume that banks don't do stuff because they're technologically inept, but I don't think that's the case. The bank I worked for was a subsidiary of the Chase Manhattan bank and as far as the hardware went they were cutting edge at the time.
Software driving products that were the banks income was extremely well documented and extremely well protected in terms of changes to the code and who could do what with it. Security was tighter than a gnats ass, both physical and network wise, with round the clock monitoring and so on.
A banks idea of disruption is not the fear of some new tech, banks know that technology only appears to move fast, they can afford the wait until something has proven itself.
A bank fears things like paypal, that obviate the need for banks and their 'products which are the privilege of accessing your own hard earned money'.
Banks have tons of special products in their inventory, the fact that you don't actually see them in the wild is that you are mostly looking at the consumer side of the operation. On the business side the special products are the majority. Then there is all the regulatory business, that too is responsible for an enormous amount of code.
For a newcomer the barrier to entry is not technology, it is simply the vast headstart that existing banks have in terms of knowledge, marketing power and financial resources.
I'm only aware of one bank that started in recent times that was not tied to another bank, and unfortunately it went bust.
Thanks for the exchange by the way, that was interesting. Who knows, maybe one day you'll found that disruptive bank based on high-technology!
I actually looked into the requirements for establishing a new bank (not in US) and the requirements were so prohibitive (tens of millions in reserve from day one, virtually obliged that no single shareholder hold more than 5-10% stake), not to mention meeting regulatory requirements like BASEL in Europe and SOX in the US mean that the big banks own the market in many countries, with no fear of swifter moving newcomers "eating their lunch". Not to mention people's resistance to change, especially with something as important as their money. And that is only on the retail banking side. It's even worse in i-banking, with the bigger investment banks making more money than ever on Wall Street, as if the crash of 2008 never happened. They may be crooks, but they have the money and influence to make sure the laws get written in their favour - see https://www.banksimple.net/blog/2010/07/21/banks-strike-back... (there was an article on HN recently around this post.)
Also looked into providing the "valuable services" you mention too, a la Mint.com (no equivalent where I live) and this is something I believe there is certain potential (you will have to build a service that taps into banks online portals and offers more useful features than the banks themselves, e.g. account aggregation, financial product comparisons, tailored financial advice etc.) I think the future is one where virtually ordinary transactions will be done online (paying bills, transferring funds), possibly on smartphones, and where you only go into a branch to get a mortgage or something major - and possibly not even then. Of course you can do all this already online, but the world is still very cash and cheque based outside of the US. It will be a while yet until the majority of people are willing to do 100% of their banking with an institution that is 100% web-based.