Hi Genny,
thanks for the reply! I think I've figured it out. I'm running Maya 2013.

I didn't have the SAVE TO FILE setting enabled in the playblast window. Someone over at CGTalk helped me out, and when I enabled this setting the problem was solved!

Very, VERY strange, can't quite figure out why it was bogging down my storage, but when I enable save to file - the problem is solved. No more GB lost.

Best,
Colby