But there have been some billion-dollar success stories. Off the top of my head, they are:
(1) Security Dynamics who invented the little token with ever-changing 6-digit numbers that you have to enter to login to your remote office computer. You probably know it today as the RSA SecurID: https://upload.wikimedia.org/wikipedia/commons/3/33/RSA-Secu...
The hardware was simple (microcontroller, real time clock, and an LCD display) and the proof of concept for the software could've been written in an afternoon by a crypto-knowledgable programmer. I genuinely admire this idea as having the least amount of technical development required to create a billion-dollar market.
(2) Paper shredders. Fellowes created a billion-dollar market for personal shredders. Seriously, before this market existed, if you told the average Joe that they needed a shredder for their home, you would have been laughed at. Then came along all the brouhaha about identity theft, and now Office Depot and Staples sell dozens of home models.
(3) Firewalls. When I first heard the concept of a network firewall--and this is going back a long time--my first thought was "What a stupid idea, why don't they instead fix the bugs that would allow you to penetrate the network?" Turns out to be a multi-billion dollar market.
(4) Password managers like LastPass and 1Password. I doubt these have reached a billion in sales, but I figure they will.
(5) Certificate authorities. An early implementation of that idea made Mark Shuttleworth into a billionaire with enough money to visit the International Space Station just for fun.
Looking at the list, the threats are sometimes abstract. I do have a home shredder, but I'll admit that it's very unlikely I'd be a victim of identity theft if I never shredded. However, the threat that Silent Circle addresses is proven worldwide surveillance, yet it's a much harder sale. It's very difficult to predict what privacy/security product will succeed.