Was searching though the userlist to find my old nickname which I forgot (dont ask me how). But there are "71884 Registered User(s)." Im guessing maybe 90% are one time posters, why not remove old names?
The problem with removing idle users is that some of them come back sometimes, such as myself. Forums usually don't come with a feature to do this task anyway as storage of old data has little, if any, negative impact on site performance.