In short; stop allowing basic newly registered users from logging on to the back end of WordPress, i believe that area should ONLY be used for the admin or editor of the WordPress, not basic users. This simple thing should not be governed by some plugin, this should be built in.
To explain further my idea;
Why not have the ability to project the users that register to a post or a page (this would keep the new user on the webpage / front end)? For example; A new user registers, he or she is then directed into a post or page (depending on admin settings) where he can see his profile and edit it (wordpress would make a new post or page for that new user or use a static / generic post or page (again, this would only be an option). This would allow for websites to build a clean user profiles, on the website it self, not in the WordPress admin area and as the admin could choose if the profiles would appear in post or pages, he could maybe control the profiles even further by sorting them into categories or allow users to choose what categories they would appear in, allowing for much more user options on material or even what members are allowed to read or do?
these are simple options that could be added and would allow the admin to manage users much better than before, hopefully, this will be added in future updates of wordpress, maybe 3.3.1? :-p well.. one can hope :)