It starts with a disingenuous comment and it barely addresses the most basic of concerns(FDIC) and does so in a snarky and somewhat rude manner.
I would think you would have learned how to handle criticism and concern for a product of yours a lot better than this working at Twitter.
My first thought when I read maxklein's comment was that he is perhaps saying it half in jest. But in case he was serious, I don't think one can just deride a person/organization based on stereotypes. (Hey you programmer of some web application, what do you know about banking, where's your suit and your MBA, you'll do a shoddy job for sure ... etc)
Let's see what they come up with and critique/praise them on what they actually do, rather than carrying prejudices.
He didn't actually give any information on what their plan entails that would remove doubts. They've said their money comes from two places loans and cuts from credit card fees. While what if they have a bad run with their loans/investments(like big banker banks) or not enough people use there credit cards? That makes them just as vulnerable as the existing banks so saying existing banks don't work doesn't tell us why you will.
Yeah, I would also be eager to see more information on their plans. I hope they would start talking more about them on their blog. I am sure they could get some good inputs if they can get a good community going. (It could be one place where his programming/OSS experience might come in handy.)
Financial world desperately needs to be fixed anyhow - I am happy to hear about folks who accept that challenge.