He already "paid up" when somehow his account info was used to buy software. What I want to know is this: If the software was purchased using his account, he does have access to the software right? Does that mean there is another user with his account playing games? I don't think you can play games unless the account…
Update. We have blocked new user accounts temporarily. We're going to upgrade mediawiki and the spam plugin, which will hunt and destroy past spam. Then we'll re-enable account creation. In the meantime, if you have an account already, feel free to add/edit.
Was the demo force-installed on your guys Steam accounts? It was on mine and 1 other friends at least. Would be weird if they installed it on everyone's accounts automatically.