[adam]

Typically, DnB involves individual samples and layered loops. Loops are selected on the basis of having similar grooves (the same snare pattern), and then are layered up on top of each other. Individually sequenced sample hits are then used to fill out the drums, and provide more variation.

This is based on an article I read in an issue of Computer Music approximately six months ago. If they don't know what they're talking about, neither do I. You may also want to look up the article...it was fairly detailed.