This is on the 2.0 list - the user won't be able to change their e-mail address without Gossamer Forum sending an e-mail to it. Of course, there is nothing to prevent someone from registering some free e-mail address, then deleting it - but I don't think 99.9% of users would go through that much hassle.
Jason Rhinelander
Gossamer Threads
jason@gossamer-threads.com
Jason Rhinelander
Gossamer Threads
jason@gossamer-threads.com