I heard Hancock was gutted by the studios, who weren't happy with the direction the film was taking - a dark examination of a lout anti-superhero - and of course they intervened. From what I've read and heard, it could have been a great movie and it has signs of it (the film was originally titled "Tonight, He Comes), but like Smith's previous flick "I Am Legend", it was patched up by bigwigs and studio execs.
I'm seeing the movie for myself later this week. I'm sure it'll pull in big bucks. But then again, it has to contend with Wall-E and Wanted, so who knows.