[masraum]

stuff that spins gets balanced, but the all metal stuff doesn't usually need to be rebalanced. You can actually send your driveshaft(s) off to get balanced, or if you get new u-joints installed by a driveshaft place, I think they often do it automatically. Crankshafts get balanced, but then don't need to be rebalanced again unless you have them modified in some way.
Tires also need to be balanced, and some are worse than others. I assume it's more expensive to make them more accurately, but even if they are better to start, it just means that less will be required to balance them. But they're still likely to require something to balance them.