I've been battling the buying addiction for a while, and I'm doing a reasonable job, though not a great one.
In July 2012 I decided that I was buying too much, both for myself and for gifting on Steam Gifts, so I decided to stop. From the end of July to the end of October I only bought one $1 bundle and one $0.25 game on Android. Then I was no longer able to resist, and slowly went back to buying. Still, at this point of time I'm resisting most purchases which I'd like to own. I didn't even buy Fallout New Vegas for $2 and Tomb Raider for $4, even though they're on my wish list.
I did spend quite a bit of money this holiday season on games ($30+), but a lot of it on Android, where I actually play games, (around $17, for KOTOR, FF4, Castle of Illusion, and Blackwell Epiphany on GOG, which I meant to play on Android but unfortunately can't for technical reasons) and $7.5 for Child of Light on the Xbox, which I play with my kids, so this is money spent on games which actually get played, and I consider that okay. I also spent $10 on game-related utilities (Gestureworks Gameplay and Pinnacle Game Profiler), which I might or might not use, but are meant to allow me to more easily play games (that's not counted in the $30).
I account for Kickstarter separately, but I budget it at (around) $25 per month on average so I won't go overboard. It's been easier lately.
Edit: Although I bought a few games for Android, I'm holding myself back there too, because it would take me ages to go through KOTOR and FF4, so it's not a good idea to make the backlog larger.
awalterj: What hole in their existence, what void are people filling?
The playing of games. At least for me. When I buy games, I interact with them in my mind at some level, learn what they're about, imagine what it would be like to play them. Then I get some satisfaction from owning them, and knowing that at some point (which will realistically never happen for 99% of them) I will play them.
It's probably more complex than this, but I think it does boil down to "I'd love to be able to play these games, I just don't have the time right now, so I'll buy them anyway and hope that I get to live forever and have enough time to play them."