DoYou2.com's failure to catch on widely may have been due to the implementation of the scheme. Its marketing focused on the teen market to the exclusion of the adult market, had a high cheese factor, and concentrated on promoting a viral e-mail system instead of the matching system. The viral e-mail system allowed users to email anonymous DoYOUs through the website, asking, for instance, "doYOU Miss me?" with the recipient having to guess who sent it. If the recipient guessed incorrectly as to whom sent it, they would send their reply to the wrong person (perhaps one of their friends who hadn’t used the system yet); the recipient of the misdirected reply would in turn try to guess who sent it (or, perhaps, delete the email). The theory behind it was that this would lead to users introducing the system to their friends, expanding the customer base in the same way a virus spreads. This system was shut down in late 2001.