It happens all of the time. Some members will make multiple accounts to back their own opinion or get an extra vote in a poll. Here's a modification that will detect and prevent multiple accounts, as well as notify the administration about multiple accounts. Inspiration for this modification came from the work of MPDev (creator of the Multiple Account Login Detector) and randominity (creator of the Multiple Account Registration Prevention). This is basically a combination of those two modifications but with new and improved functionality.