There are certainly different ways to look at this. Some people believe a All Star game should consist of players who had great individual success throughout the season. Others believe a team's wins and losses should play a large factor in who gets selected. I'm of the perspective that being selected to an NBA All-Star game is completely attributed to random whims.
If the Pistons are being rewarded for great team play (as they should be) shouldn't Z also be rewarded for being the only other consistent source of productivity for a Cavs team that has won plenty of games? If you would excuse a little hyperbole, doesn't this logic also mean Chris Bosh should be penalized for his team's poor play and consequently shouldn't be on the roster? There is no consistency from the league on why a player is selected to the All Star game, therefore I cannot evaluate whether or not a player was actually "snubbed".
That said, Rasheed is having the best year of his professional career. His assist to turnover ratio is very low for a bigman, he creates plenty of opportunities for Billups to get into the open court with blocks and steals, and he shoots from the perimeter as well as a small forward. His rebounding has been streaky, but his team hasn't lost many games due to lack of rebounding.