One thing that needs to be considered when talking about registration is the number of people "passing through" who sometimes start an interesting thread or make a valid contribtution. These people may not want to register (at least until they get the feel of the place) and may decide to go to more "open" places.

The question is: is it worth risking losing a number of good contributions simply because there a few people trying to spoil things for everybody?

Also, and I don't know on this one and it is not my problem but the time and effort involved in setting up such a system may be an issue.

Jon