[quote=@Bishop]
[@Spanner] Isn't account selling and trading a common thing in every mmo although illegal? I mean, besides putting the password and username to login, how would they know it was you?
[/quote]

I don't know exaclty how they managed it - since it was never specified in the novel - but it's said that it is a single character for player and it was impossible to create a second character, making selling accounts quite the impossible thing.

Also, YGGDRASIL has an exclusive console and stuff like that, so it isn't far fetched to guess that they had a way to recognize the player to make using other's account impossible... Not really sure about how though.