There is a MASSIVE thread about this on dogsonacid.com

Seems to quite the in thing now to generate your own kicks (and other drums) in an audio editor... The results are pounding when you get it right too. No dodgy phasing, no softness and no shitty sample sound, just a good solid TUNK! that you can rely on to rock it.

Combined with a sub sine generated in the same way, tracks have a massive low end drive and purity...