Loads of people live on their PC's.
Sites like 2nd life have made millions praying off those shy and insecure folk who once have an avatar on 2nd life can be whoever they want to be. Whilst the concept is great Mike, people are very false, where there avatar may portray them as Young Hansome and fit, in real life they are probably the opposite.
The danger happens when people get mixed up with real life, and thats when the problems happen, the divorces happen and people generally start getting hurt big time.
There was even a mention that Al-Qaeda was rercuiting Suidice Bombers on 2nd life
Dating online, but not actually meeting the person is well strange, Its almost on the verge of Adult pretense, and people just doing it for a trill, and like 2nd life, may be totally the opposite of what they discribe themselves.