<DM Turbo-Rant Mode On>
You know, DMs wouldn't even need to run DMPCs if there weren't so many gamers out there who want to PLAY the game, but never want to do the WORK of running a game of their own.
Did it ever occur to any of you DMPC haters out there that maybe after spending hours and hours of prep time, and hundreds and hundreds of dollars on books, adventures and miniatures, that the DM just might like to be PART OF THE GAME and not just your own personal World-of-Warcraft-substitute, thanklessly running encounters so that you and the other players can have the fun of "dinging" another level?
Name any other social situation where someone makes an effort to prepare a fun activity for a group of friends, only to have people complain when they actually try to join in on the fun? Think about spending a week planning a party for all of your friends, (food! games! decorations! party favors!) and when the party actually starts they all turn to you and say "what the heck are YOU doing here?"
If a Dm's DMPC is really bugging you, why don't you offer to run the game for a while so he or she can PLAY? Don't want to run the game? Then shut the flumph up about the DMPC.
Frankly, everyone who plays D&D should spend half of their time running games as a DM.
I'll say that again.
Everyone who plays D&D should spend half of their time running games as a DM.
If your time as a DM is close to zero, if you're playing and playing and NEVER doing any of the work, then you've got NO RIGHT complaining about how a DM runs his game, or the fact that he chooses to let his or her own PC join in the fun.
You don't like the DMs DMPC?
Run a game for him to play in, or go find another game.
<DM Turbo-Rant Mode Off>