I have seen the same problem since the MobileMe launch, but had no previous problems with the old .Mac service. I also have two iphones, but the problem at least for me seems to come from the MobileMe servers, and then it spreads to all of my devices.
Yesterday was the worst, about 10 or 15 contacts were repeated 20-40 times (I counted one contact that was in there 46 times. I didn't bother to count the others). And, to add insult to injury, all of the photo images of my contacts are now gone.
MobileMe syncing is still very buggy, much too buggy to be a paid service. I wouldn't be terribly upset if it was clearly labeled "BETA" and we were told that up front. But basically, we are paying to be beta testers for Apple. That's not cool.