Possible explanation for some hacked accounts

The strength of my passwords greatly depend on what it's being used for. My bank password is over 10 digits with numbers, letters and special characters. My "email that I don't care about that I give whenever something absolutely requires an email to sign up" password is much, much simpler.

I haven't gone to RockYou, but to be fair it sounds like something that wouldn't warrant a second's thought.