My ST4S has over 12k on it now, and is on the original chain. It still looks fine to me.
I also normally ride with a pillion, and am not shy on the throttle/brakes. I do have a scottoiler though (since about 3k old) with a dual tip feed (viper ?).
I recall someone mentioning in a post of a 'chain guide rail' that bolts in front of the front sprocket, and stops the chain smashing casings if it breaks. I think this might have been in the 996 forum (possibly age996's thread). If I can find the post I'll try to post a link to it here. Has to be a good idea if it saves a lot of trouble for a small outlay.
[update]
sorry lads, just seen this was discussed in the other thread. Doh ! \I'll head off back to me corner and keep quiet...
[Edited on 10-8-2005 by John W]