I got bored of WoW during vanilla once I had been max level for a while. About 6 months after BC came out I decided to start playing again but this time as horde. I couldn't decide what class to play. I remembered this guy who was in my guild in EQ2 who 2 boxed and I thought I'd do something like that so I could level 2 classes at once.
I honestly just thought I'd have an alt follow me about and leech xp but it would still be quicker than leveling twice. A google search later and I had found this site and was amazed that so much more was possible. Couple of weeks later my 5 computer setup was complete and I was running Pally and 4 shammies.