Insight Driver - the stories come in two (similar) flavors: 1) speed wobbles, where the front wheel starts to slalom back and forth (this is what happened to me) and 2) trailer tries to overtake the bike. This might be the same thing. I heard it described as the tail wagging the dog, and also as the trailer trying to steer you, instead of you steering it. Someone i talked to a couple of days ago described the speed wobble very well, I can't do it justice, but basically he said the trailer would go one way, pushing the front wheel the other way. When the rider tries to correct it, the trailer would go the other way, and the same thing would happen on the other side.
what i remember from my experience was that i got a little wobble going, and it just got bigger and bigger, the front wheel swooping farther and father in either direction... i tried to brake gently, not wanting to do anything sudden, but it didn't work. the same swooping thing happened to me earlier in that same day, but gentle braking brought it under control. i can't really analyze it any better than that - it all happened pretty fast. i just remember thinking "i'm going to crash" and then i was waking up on the side of the road. the day i crashed i had about 10 extra pounds of food & water from what i usually carried, because we had about 70 miles with no services that day.
oh yeah, for full information, i was riding a hard-tail titanium mountain bike, with a locked-out shock, carrying a fairly light handlebar bag and towing the trailer.
The bob instructions (which I read after the fact, d'oh!) say you should not load it heavier than 70 (??) pounds and not go faster than 25 mph. I think the combination of heavy load and high speed is what got me.
oh, and if you do get a bob, get some spare cotter pins and some duct tape to keep them attached... what a stupid way to attach the trailer! those pins just disappear with no provocation.
to be fair, i have also heard of and met lots of folks who really like their bob trailers, and don't feel it affects the handling. as for me.... i'm about to buy a real tour bike. racks and panniers all the way.
valygrl