I started dual boxing not so much to level two toons at the same time but because my 2nd paladin was getting ganked perpetually. I already have a well geared 70 Paladin on Laughing Skull [H] and had a lvl 11 Paladin on my second account that was originally created to be a twink. One day I came across a levelling guide and decided to test it out and couldn't believe how fast my lowbie pally was levelling. Then I got to STV and the misery set in. Out of necessity I decided to start dual-boxing more or less to protect my lowbie pally and have set him up paired with either my 70 paladin or my 70 hunter depending on the environment, usually hunter in the wild and paladin in instances.

The best thing I can see that prevents me from getting ganked now is that the names of my two paladins aren't similar. I kinda think the whole namea nameb namec thing is cool, but it makes you a target IMO. Since my paladins are named Persiphonie and Rhadamanthus they usually don't get assaulted when they're running together. My 3rd paladin on my son's account is named Bublnhearth, so even with the three of them together, the unique names may prevent them from being a kill on sight target.

[ atleast until now, since I gave away all their names. ]