I have been watching this thread closely and was not happy to see that as guys started pulling axles, they were finding issues with the bearings. No offense to the OP but it would have been nice to see just an isolated issue.
I fly airplanes for a living and any issue like this would have triggered an Airworthiness Directive forcing all operators to check the bearings. I maintain my bike like I would an airplane, so immediately went to the dealer with this issue.
I could have checked this myself but went to the dealer for several reasons.
1) They are only 20 minutes away.
2) It will now be on record that a customer has had a complaint about the rear bearings. ( none of this hmmmm, we have never heard of this before ) If they find an issue, that too will now be a matter of record for any others who may have an issue.
3) Replacing the bearings myself with an aftermarket set, may only serve to cover up a greater issue. The problem may not be the bearing. So even with new ones, I will still be inclined to pull the back wheel and check every so many miles to make sure.
4) If enough people report this issue to BMW and they begin to see an issue, they will hopefully come up with a permanent fix or recall.
My dealer was great. I told him of the possible issue. Explained how I came to learn of the issue and was quite prepared to pay for them to check. They wrote up the service order with a " customer feels vibration in back wheel. Please check bearings, particularly the one closest to brake rotor." He said this way, it would be done under warranty, no matter what they find.
Can't ask for better than that.