Hey Cobbs,
I'm a multiboxer myself, Used to play 5 to 20 characters LIVE - I moved to free servers because my time is limited, and i really enjoyed WOTLK - it also helps me to relax after work for few hours- now as far farming, multiboxers usually dont farm. they do quests, which requires to do on all characters and be completed, think about playing single guy, you have to do 5 times same quest , depends on a quest, unless its a slain quest. still it takes some time and dedication to level all to 80 (as wotlk server) multiboxing is not that easy as some people may think it is, we use legal program called ISBOXER - which we pay for it.
I see people getting banned left and right (you know RED popup) people that actually cheat.
Why do we even multibox? its a hobby really. we do not level to stay @ spot and farm alliance or horde. vice versa.
While leveling (me at level 67 atm) I got wiped so many times its not even funny, some people think its easy ones they see you at level 80 flying around. trust me its not on PvP servers. *you get camped to death* and its fine. you go afk and do some things IRL.
Think about multiboxer as one big guild. that have 5 to 20 characters online and they do same questing, instance runs , etc.
Now the only problem as I could see (as multiboxer myself) for example standing in stormwind and wiping people over and over, guards , etc. so people cant turn their quests in, etc, same thing could be as a guild with 20 players online rushing through ORG.