The next time you find yourself pounding your keyboard in frustration because the domain name you want is already taken, direct your ire toward Mike Mann. Mann is one of the longest members of the clubby world of domain speculators, and he's buying up names in force these days. And not all on the aftermarket, as some others do. But new names. Dot-com names that aren't registered -- even though 100 million-plus already are -- that he then turns around and sells for a few hundred bucks, sometimes far more.