That's fair. However I'd argue that someone implementing their own algorithm would not use a library like keyczar. They would just write their own. So while it

That's fair. However I'd argue that someone implementing their own algorithm would not use a library like keyczar. They would just write their own. So while it's possible to write your own and be secure, IMHO it'd be better to stick to vetted algorithms and libraries... I think it's just that - all other things being equal - the public algorithm is more likely to be more secure...