Convertible debt paperwork is really only a few pages... Heck, they might've used YC's boilerplate docs to simplify things.
I trust Paul implicitly, and I suspect most YC Founders do, and that probably has a lot to do with the acceptance rate. I wasn't in the meeting obviously, so I can't know how I would have reacted to the specifics, but I can say knowing only what I know now I probably would have at least taken the weekend to do my homework.
Edit: phrasing.
What rational reason would an angel investor have to avoid investing in a company that has taken this investment?
(Or he might die of a heart attack, or the Russian government might seize his assets, or any number of other unlikely scenarios might make him unable to close the deal.)
Actually, the TC article says many of them signed papers at the offer meeting itself.
I understand the offer sounds fantastic, but surely they'd want some advice first?
Obviously they didn't, but it seems a little rash.