I'd rather Mint be hacked than my Bank of America login.
Because someone can't do anything with my Mint login, besides delete data (not affecting anything - it'd still exist on the appropriate bank site).
If they have my B of A login, they could transfer money.
Besides, if Mint is hacked, I wager that it'd be the Mint username/password combo itself, not the ones for the institutions that are hooked up to it.
And finally, I think there'd be a disclosure so fast I'd easily have time to change the half dozen passwords on accounts linked to it. If they hack some of the account accounts (out of all of the accounts there), the odds of mine being in there is small. Even if they hack a million of them, and mine IS in there, and was in plain text for some reason the odds that they then get access to my accounts and transfer money (while going through those million) before it's discovered and I can change passwords is small. Further even if it DID happen, most likely the bank would recognize the fraudulent attempt and block it. And even if they didn't the odds that I'd be liable for that fraudulent activity is small.
All of those tiny, tiny probabilities put together? I'm more worried about dying from an asteroid falling on my head than I am of losing money because I used Mint.
Here's the thing: since it's dealing with money, there are disclosure laws Mint has to follow. AND it's something people will notice quickly. So if if they were hacked, and Mint didn't know, once people started losing money, we'd find out fast. And at that point, you can change your passwords. The odds of you being one of the very first to have your password cracked from Mint's database is exceedingly small.
I think if Mint is hacked, it I think the most likely look like this:
Hackers gain database with logins and passwords (to Mint itself, not banks that are hooked up to Mint). It's encrypted/hashed/salted/etc. Mint announces this, everyone changes passwords Mint, and to their banking institutions (just in case). No accounts actually lose money, no reported losses. Mint's reputation takes a hit, everyone moves on, most continue to still use it.
If you aren't comfortable with it, fine, no big deal, don't use it.
But trying to convince me it's not safe? Heh. Sorry, I'm not worrying. Because even if they are eventually hacked (which very well could happen, I'll grant you), I think the odds of losing any money are so exceedingly small it's well worth using the service.
To each his own, YMMV.