I wouldn't really call it trolling. There's no intention of malice, he doesn't feign seriousness when making a controversial point, he is very self-deprecating, and everything is said interspersed with jokes (that of course are sometimes hit-or-miss).

In many ways, I think he uses one of the best techniques for coming up with new ideas and provoking discussions: asking questions (even ones that seem stupid at first -- and sometimes later as well), suggesting thought experiments, using humor, and above all, never taking yourself seriously.

I say he trolls sometimes because, if I recall correctly, he's said that he (at least once) has made a post he doesn't agree with, so he could see how people responded. I'll see if I can find the post where discussed this.

I guess that's either trolling or performing a psychological study.

Edit: the closest I could come is "...I enjoy yanking the chain of people who think they believe things for actual reasons as opposed to taking a side." Which isn't very close. It's in an interview with him at http://freakonomics.blogs.nytimes.com/2007/10/31/scott-adams... (Look for the second-to-last question)

Second edit: Found it! "As regular readers know, I sometimes like to make arguments for positions I don’t hold, just to test my viewpoint." (http://dilbertblog.typepad.com/the_dilbert_blog/2007/12/next...) That's...actually not as damning as I remembered, given that his motivation is "let's see how logical I really am".