I've wondered myself about the 'long' oil change intervals on the new cars. I've always been a 3-5k miles type of person.
I can't imagine that BMW, Audi, Mercedes, etc. haven't put the research into this matter, prior to making the recommendations. Considering that they are aware of US laws and class-action suits, I'm certain that they have reems of documentation confirming that the recommended intervals are okay.
The real reason for the extended service intervals, of course, is to save them money. All of the German manufacturers are 'Free Service for the first XXXXX miles'. They probably went to less frequent changes with higher quality (synthetic) oil, in order to reduce the number of trips to the service department, for each individual car - reducing the strain on the dealers service departments.
Because I was a little nervous with the long interval in my car (13.5k for first change), I did research on several forums (MBWorld, BenzWorld, BenzForum, VWVortex, Club B5, etc.). Several people reported having sent oil samples for evaluation after the 'long' interval.
In every case, the analysis showed that the oil was still performing as it should, and there was no observation of excessive wear.
Although I am still uneasy with the extended intervals, considering that most German manufacturers are now recommending Mobil1 + long interval, and the oil analysis results show no problems, I'm getting used to them.