Would starting up a sort of gmail (googlemail) exchange site be worth it? Would I get enough members if adverised properly?

Thank you,
Jezzo

It's hard to say, there are already a couple of them out there now, hopefully it doesn't become a trend.

The main concern I'd have is that the site would virtually die overnight the day Gmail launches publicly.

Why would they die over night? I mean, if you get a large community base, you could have people who want to trade because they dont like a username.

I am neutral in this conversation, but I just wanted to point out something.

I personally don't think there would be a large enough community to warrant the trading of usernames post-launch. The only reason there's so much interest in acquiring an account is because it's the latest "thing to have" (@gmail.com), which will quickly level off when it's publicly available.

People aren't after the names as much as they're after the account itself.