I need to canibalize because I'm a lazy bastard who's not all that motiviated to draw stuff up from scratch. That and I've a talent for taking premade stuff and making it very much mine own.
My campaign wouldn't have gotten far without Dungeon Magazine, that's for sure.
Even when I run premade adventures there's still a good bit of "changing this and that" to make them conform to my campaign.
I understand WotC is releasing some new mega-adventure(s?)...should be interesting.
I used to just take parts from modules: NPCs, maps, that sort of thing. Lately, though, I've been running more modules wholesale (even have an Age of Worms campaign started up).