I think in an extreme case using a moly grease in a wheel bearing could cause the parts of the bearing to not rotate and create flat spots, but like someone else said, greases have come a long way.
As @-Spike- said, the old tale of moly being so slippery that is causes flat spots goes against the laws of physics. I can only see this happening if the moly grease is too thick--so thick that the rollers can't rotate. If the moly grease is rated for wheel bearings then it should absolutely be fine.