Interesting topic.
It goes without saying that all the players deserved to be penalized, Artest the most. Zero question there, he stepped over the line in a huge way. I think a full year is probably over the top, but whatever, the relative weight of the penalty is open to individual perspective and opinion.
I do think that the NBA needs to think about slapping fans with penalties as well. They can't fine fans (no authority obviously), but they can suspend them from games.
Take the fan that threw the drink that set Artest off (no, I don't think it's even remotely reasonable to say he's an innocent), he shouldn't be allowed back inside an NBA game for some period; the rest of the season, or longer if the event shows a pattern of problematic behavior. It would be elementary to enforce, and a minimal expense for the owners. Cameras at the gates, the software to scan faces (it's all over the place these days anyway) and a single security employee at the facility to monitor and alert staff as appropriate. If you get banned, then you don't get to go see the games.
Fans may be the ones who provide the money that pays the players, but that doesn't give them carte blanche to act any way they want, demean the players, etc. Yes, the players are the professionals, but in as much as they have a responsibility to act professionally, so too do they have an expectation for reasonable treatment. A player can expect to get heckled, jeered, ribbed, even verbally abused above and beyond what most would consider acceptable behavior -- but even animals at the zoo shouldn't have to endure some jackass throwing food and/or drink at them, let alone batteries, bottles, etc. Why should an NBA (or NFL, or MLB, I'll leave the NHL out until they decide it shouldn't be sanctioned boxing on ice) player? He's not being paid to be abused, it's part of the package, but there are limits to what they should be expected to endure.
Which is not to say it even remotely excuses going into the stands, ever. No matter what some fan did or didn't do. But having balls and at least some pride, I can understand (just not appreciate or respect) on some less evolved and unrestrained level why Artest did that. He did it though. He screwed up, he's getting slammed, so be it.
I'm just saying that the fans should suffer consequences for their actions as well. Barring them from the games they hold so precious would be at least some incentive to not throw things or take to the court next time.
Just my take though.