Love the idea! Definitely in! Here's a solution to mitigate the long term risk:
What you could do is group people by birthdays that fall in the same month and arrange it so that they bomb each other anonymously. That way, you can even add and drop people throughout the year. It's a lot of coordinating from your end, but I think it could work. You can even sort of time it like Geek Critiques and say "Mid-November" post a thread asking who's interested to participate in the "December bombing," get the bombing list out by the end of Nov and sit back and watch it unveil during Dec. Just a thought, hope you go through with it!
P.S. If you do like the idea, here's a few proposed rules. To make it even more anonymous, discourage ppl from posting in the thread and have them PM you instead, while you keep posting in the thread of how many slots have been filled for that month. I think anonymity just adds to the fun imo. Also, to limit you having to work endlessly, maybe have a limit of 10 slots per month. That could serve 2 other purposes, keep it enticing and also garner only the very interested folks who are responsive and reliable. And lastly, if the bomb photos are posted in that month's thread, that'll make for a very clean and organized system. Btw, sorry for rambling, the idea just sparked my interest and got me thinking.