We've written a lot here about offspecs, and it seems that with the Burning Crusade, players who choose to offspec are finally getting their due-- druids can play as rogues, shadow priests can play as warlocks, and dual-wielding shaman can play as fury warriors if they want to.
But there is one problem. Some players are, unfortunately, forgetting exactly not what they're supposed to do, but what they can do (excellent rant there, definitely worth a read). If you're a shadow priest, please remember that it is possible to get out of shadow form and heal if necessary. You may be a feral druid, but sometimes it's time to step back, drop out of cat form, and heal. And sure, as an enhancement shaman, you may have loaded up on strength, stamina, and agility rather than +healing, but when the healer is going down fast, every bit counts, and it's time to get out Lesser Healing Wave and start spamming.
I don't mean to force you to only do things you aren't specced to do-- if you're shadow, and someone asks you to main heal an instance, you have a right to say no. As I said, we here are all for offspecs-- they break the cookie cutter molds built around characters and show us things in this game that have never been done before. But in this case, necessity is the mother of non-invention-- if necessity calls you to fill a traditional role, even for one fight, please, fill it.