My initial gut reaction would be that it's their fault for leaving their bikes laying down on a mountain bike trail where, by it's very nature, people would be riding mountain bikes. Especially so on a red/black run where people will naturally be riding faster.
Unless they had a very good reason for their bikes to be there (ie. if they'd both fallen off them), then there's no excuse. If you're not riding your bike on a trail, move it to one side so that others can. You wouldn't just park your car in the middle of the road, so why should it be any different if you're out riding..? It's selfish and it ruins it for others.
You could argue that ajantom was riding too quickly, but then again he was on a red run which is designed for that very purpose so I don't think he's doing anything wrong. It's the two ar*ehats who decided to create the temporary roadblock which is the problem here.
Personally I think the guy is lucky to get away with a taco'd rim and not a taco'd nose.
