It will work, as long as it's locked by mods instead of making it an open thread. Have a separate polling thread so people can nominate members. Than once the poll closes, a mod can make an official stickie or something and post the person that won the Member of the Month deal. Then it gets locked again. It keeps it clean that way and tightly regulated. I'm all for it.
I've seen this on other forums and it works. Make a special section for the Member of the Month to make a big deal out of it. Check out this forums member of the month. You'll see how it works:
Use that as a guide if you have too. Yeah, that's my Corolla forum.