In any given song, when is cool for the bass player to "go off"; that is, stop what you were doing for the groove and start embellishing the crap out of what you're playing? Is it ever okay to go off on bass? More importantly, is less actually more in terms of bass?
This is a very hard question to answer. Troll any bass player forum and you'll see many a flame war about this topic. Guitar players and keyboard players perhaps don't have to think about this as much as dudes holding the rhythm - but they really should. It is definitely one of the most important things to figure out for any musician. I'm not sure I completely have the answer for myself, but I definitely know when a bass player has gone too far. This will certainly be a topic I will revisit in the future, but I hope you will swing by and check out this entry at Ryan's Blog. My jaw hit the ground when I saw the clip that accompanies the entry. This guy is using one drum. One. Yet what he does on that one drum is infinitely more interesting and groove oriented than what Carmine Appice is doing on his gazillion piece drum kit.
Anyways, check it out. Ryan is a thoughtful blogger and the digs at Terry Bozzio* are hilarious.
* - Did you watch this clip? It'll really tax your ears, man. Like I said, drum solos might be the only thing worse than bass solos.