Well that's fine, but what about the folks who've opted to be emailed when they receive a new private message?

That's one of the reasons why I think this should be a hack or plug-in, as opposed to added to the main distro. If you have a group of friends or acquaintenaces that you choose to send email to from time to time, you can just as easily add them to your browser addressbook and send it that way. Giving them the option via PM is a good way for someone to log in and randomly start adding people to their spam list (much easier and quicker to click a username than it is to go through each username and grab their email).

Anyway, I don't like the idea either. There are always pros and cons against I suppose.
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<a target="_blank" href=http://myth.jccc.net/wwwthreads2/index.pl>Screamers</a>

That would clog up all your server storage space.