I go through spokes like fricken candy. Funny you should bring this up... I just broke a spoke on my front Ksyrium ES this morning... second one on the same wheel, which was rebuilt after being damaged in an accident last year. This wheel has about 1,400 miles on it since being rebuilt. I broke a front spoke on my Roval and had the whole set replaced under warranty because of cracking eyelets. I broke the carbon spokes on my R-SYS on two occasions, once scraping a curb and once on impact with an obstruction in the road. I also broke a spoke on some crappy ALX front wheel I had that I was using while getting my R-SYS fixed the first time. I've had pretty good luck with the rear, I only broke 4 NDS spokes on the crappy wheels (built with alex rims) that came stock on my Allez Sport. I got frustrated with those stupid wheels and bought Ksyrium SL's to replace them.
It seems to happen with greater frequency on pre-builts....no matter what "level" they are.