1. The game may be on sale. For example, I bough Shin Megami Tensei IV because there was a promotion with Fire Emblem. I intended to play it, but still haven't gotten around to it.

2. I start off one game then become bored or get distracted by others. Pikmin 2 and Lego City are examples. I liked them, but then Bioshock came along, and I started playing that, then I got Fire Emblem, then Mario and Luigi...

3. I get stuck and frustrated, and by the time I get back to a game I've lost my place and interest. I swear I'll beat you one day Chrono Cross...

4. Impulse buys. I heard so much about Okami, and there it was on the shelf at Gamestop. I bought it figuring I'd get around to it. Never did.

So lots of reasons I have a backlog. I never bought anything KNOWING I wouldn't play it, but wanting to play doesn't always translate to playing.

Definitely time.

I keep a list of games I want to play and generally do not buy them until they hit the $10 - $20 mark. As soon as they get that cheep I buy them and they go on the shelf. But unfortunately the backlog keeps growing, because gaming is only one of the things I enjoy doing outside of work. So I most likely only game one evening a week, unless I get really hooked in a game then I will try to make more time.

As for replayability, this use to be important to me when I was a student, but not so much anymore. I would prefer to go through a game once and move on to the next. I hardly ever touch multiplayer, unless it is a way to play the main campaign in co-op.

School prevents me from having adequate time to play games.

Playstation Plus gives me a backlog. True that many of the games I would not have played otherwise (such as Saint's Row 2), but I want to get the most out of my subscription. I try only to buy games when I know that I probably won't be able to get it cheaper anywhere or anytime else. Steam sales are a good example of this, and explain my huge PC backlog.

I buy games because I think I will have time for them, but then I don't. Maybe I can play them once I'm retired.

Too many good games, too much money, and not enough time.

I think many people plan on actually playing these games. But, real life can just get in the way and people run out of time. In the past I didn't normally keep a backlog of games but with digital games etc. I have a acquired a nice little list of games I have yet to play due to not having the time.

I find a good deal, buy the game, but then it turns out i don't have the time to play the game. Some games also suck and i am stuck with them because they are digital. When they have the complete GTA pack on Steam on sale for €5 how can i not buy it. Well it turns out i have no interest in playing these games and so the backlog gets bigger

And spend too much time on VGChartz... although that's something that can be said for almost all of us .

I never understood the practice of buying more games than you have time to play, unless you have two absolute must-haves releasing in a similar time-frame. Given the lopsided nature of the industry and its release schedule, however, i could certainly see accumulating a backlog in Q3/4, but it should certainly be eaten through by the following May or so.

Fine, it's only me

for me its time... and the fact that i am a slow gamer... i always exceed the time of a standard play trough. also, like to collect all the trophies and do some weird unlocks some games have... i buy games, almost every time on sale, so i am not a big spender, but the games do pile up... PS+ is killing me too, several good games per month and only time to finish one :(