what kind of gambit is this?

domination of the center

I see this post is kind of old...no one has given you much positive feedback on this idea of Qxd4, obviously because no one has studied the lines.  Normally, the queen after Nc6 will retreat to e3, where she is flexible enough to travel to the kingside.  Do a bit of research on it and see if you like it.  It isn't fair to just say, "generally white gets punished"....generally speaking can mean anything.

The Ruy Lopez was not a valued opening at one point - the King's Gambit was much better, but now the times have changed.  The King's Indian used to not be a good opening, but now times have changed.  Same goes for countless openings, where a genius all of a sudden figured out how to get a decent position...how about the Petroff...useless for centuries I believe, until petroff discovered 3...d6. 

Please, chesschamp, take my advice.  If you don't get any good advice here, keep looking until you find your answers.  I will give you a link to some cool ideas in this opening...

http://en.wikipedia.org/wiki/Center_Game

http://www.chesscafe.com/text/kibitz103.pdf

It may sound funny, but Tim Harding, who is a regular writer and great player, notes that the move was a surprise to him...2.d4! Good surprise value. 

Here is another note: If you study the opening, you will see that you have SO many playable options after e4 e5 d4 exd than just Qxd.  You could easily have 10 openings to pull out of a bag and trick your opponents, including the Scotch Opening and Gambit, The Danish Gambit, etc...

My advice...play it and love it!

thanks alot