Yes its true lot of new users get banned. reason is they do not read the rules properly. every one is not familiar with the forum environment, and wat i suggest is below A pdf or ms word file to download for new users to study it properly. A simple test which would have random set of questions related to rules. Allow access to members once they clear the test.
The infraction system works quite well as warnings actually... Requiring people to take a test probably wouldn't be a great idea.
it could be a part of registration process. infrations are best agreed, but prevention is better then cure
absolutely, even i wont, but if the forum is best every one would do that , it could reduce lot of work for moderators, i hope vbulletin comes up with such a option that would reduce your work too . could be 10 random questions select the right choice and you are done out of 6/10 correct answers user registers and enters in. This should be done as no of new registrations are growing rapidly, you mite have to think on it sooner or later.
No, I don't think a test would do the job. You stated that this forum is the best, and to be quite honest, Digital Point is in the close running of a few sites, with SitePoint varying slightly. Making users take a test would be insulting their intelligence, and they won't join. As for the pdf or word file, all the rules are online in one area, it's not that hard.