I can GUARANTEE, with 100% certainty, that you've heard at least one of their songs.
I think one of the reasons people dislike them so much is that they're a marketing machine. Their music is literally everyone -- commercials, teasers, before/after sporting event commercials, video games, etc, etc. I was playing NHL 10 and one of their songs plays in the background! Chad Kroeger is a business genious, albeit not a great musician.