You know, I ask this question all the time. People who "hate" Nickelback just seem to be doing it blindly. I like a lot of different types of music, and have been listening to Nickelback for years. What always gets are me are people who will say something like: "I hate Nickelback. Oh, but I love Theory of a Deadman!"
Oh yeah - because it's IDENTICAL in every way. Chad Kroger from Nickelback has even recorded some songs with that band. It's just crap. People always need something to hate on, and it's always the mainstream. If everyone really hated them, they wouldn't be one of the best selling rock bands of all time.