phpp is a step backwards.... but it is free... As for using the users table for another use, I fail to see how the database is copyrighted by vB and it would be real easy to write a schell script to copy the usertable over to a new database....
I still say the biggest hurdle is the passwords....
As for why... say you have a few X-rated members on a PG content website.... you get the idea and even with pivate groups there are things I don't want associated with my site in anyway or form....