You will notice all of the different variations of NWN I own, along with the new "Diamond" version. I recently made a post about this in my forums on why this is the case: http://www.ihatedrm.com/cs2/forums/thread/28.aspx
Note also that I own the same copies of other games as well. I sometimes buy the "Gold" or "Plat" version just to get everything consolidated. Basically, I am a very, VERY, good customer. The type of customer game companies LOVE.