There's something reassuring about being one user drop in an ocean of millions, as I am in GMail.
There's a reason they pay more (a lot more) for car insurance, and it's not because risk assessors are playing the age card. It's because young men are more risky.
(Of course, this also means they're much more likely to take the big risks required for entrepreneurship -- a tendency to risk-taking is not an unqualified bad. I think it's an essential quality. I just don't want to fly in planes flown by 19-year-olds, and I don't want them in my mail spool.)
I read the security page, and while I understand that there are "safeguards" in place to say that the founders can't read my email, I find that kind of like me saying that I can't browse porn because I installed a porn web browser filter on my PC. I have all the passwords, so I can choose to turn that off at any time.
If I sign up for your service, your servers contain plain text copies of all of my data. If it's not in plain text, then it's encrypted with a key that you hold so you can decrypt it for indexing.
I think there is a market for technology like this, but I think it would be more turnkey solutions for businesses so that they can own and monitor access to their servers and data. Is this a direction you are considering?