A friend pointed me to Ishkur’s Guide to Electronic Music. While informative and chock full of samples for all genres, it’s also quite sarcastic and funny. Here’s how he describes IDM (intelligent dance music):

This is the oddest named genre in the entire world, since it's not easily danceable, it's not certifiably intelligent, and it's arguable as to whether it constitutes as actual music. This is the realm of the uber-pretentious electronic music afficionados, with razor-thin eclectic tastes, who spend most of their waking energy arguing about what IDM is and what IDM isn't. But I guess that depends on what your definition of 'is' is. That's why it's the one genre that doesn't have any kind of cohesive sound. That's also why some of them despise the term "Intelligent Dance Music". So just ignore them. It is fun to listen to, after all.