Yes, there are massive economic inefficiencies in the whole mortgage lending business and since a16z's motto is, "software is eating the world", there are opportunities for tech startups to disrupt all of that.
To spur discussion, I'd categorize "disrupting mortgage industry" into 2 general buckets:
(1) disrupting the procedural aspects of a mortgage : lowering the cost of moving the transaction from the "loan application" all the way to "closing". The worfklow aspects.
In terms of disrupting people, this means disrupting the loan officers at banks, appraisers, title searchers, surveyors, etc. In terms of disrupting "fees", this means reducing/eliminating "loan origination fee", "title insurance", and "survey costs". (A lot of these administrative overhead costs are basically a bunch of "checks & balances" to ensure the loan transaction is not fraudulent or has undocumented liabilities ... e.g. verify loan applicant's paychecks to make sure he/she really has a job with $x income, and the property's recent newly installed fence doesn't encroach on others' property lines creating a potential lawsuit.)
(2) disrupting the loan underwriting : This means lowering the cost of money. Today, we see that a 30-year mortgage in America is about 3.7%. Maybe there's a market inefficiency and a clever entrepreneur can lower it to 2.5%.
The vastly different problem-solving aspects of (1) and (2) will attract very different skill sets. E.g. entrepreneurs interested in (1) might think of reducing costs of surveys with robots/drones/satellites while startups interested in (2) might try to lower the "cost of money" by creating financial packages such as "500 co-signers on a mortgage that also receive a portion of the profits from the house's sale."
In the video, he mentions FNMA and FHMLC are the ones that buy home loans. Basically, it means that banks like Wells Fargo and JP Morgan Chase are glorified order takers. They charge a $1000 "loan origination fee" to sell your loan to the the government sponsored agencies. If the loan ultimately ends up at FNMA anyway, maybe there's a much cheaper way to accomplish that. (Although I doubt the FNMA website will ever have a landing page that says "Skip the banks and apply for a loan directly with us!")