When people use this forum just to get their homework done for them they should at least be prepared to return here and check for replies. So many people seem to post a question (and register as members) that are so impatient that they expect an instant detailed essay, and if they don't receive one clear off and never return again despite people spending their time to write one.
Could you by any chance put a compulsory question on the registration page about what the persons' reason for registering is?
If they say they are asking a homework question they should be allowed to register, but if they don't check for replies within a month, their membership should lapse. Perhaps the same should apply to members who don't post at least one message a year.

