Riding back from Sherwood pines i thought my bike had exploded, i can't give a better description, i've never heard anything like it. In a split second there was a bang that i felt in my arms and i expected to see the floor come rushing up towards me. I managed to get my feet out and luckily my ass was forward far enough to avoid an injury that doesn't bare thinking about, i thought my frame had snapped, looked round in a frenzy, no obvious damage apart from a missing saddle...that was 10 yards away in the road.
I got the post off someone on here (can't remember who), and remember him saying 'check it from time to time, they tend to work loose' i also remember the same thing happening to someone else. That's a major design fault and i would advise anyone riding one to chuck it in the bin (or put it on ebay quick). If you're thinking of buying one cos they look sexy...just don't. Ten minutes later someone pulled out on me when going at 30mph but it wasn't as scary as riding on a USE ALIEN seatpost.
Same thing happened to me.