I have 5 accounts, with one of them being my teenage son's (well, when he has the grades to justify having his comp). I use his account as part of my boxing setup when he's not playing, and sometimes he even runs my 5th man (btw, that really messes with the other side ).

I merged my 4 accounts into one B.Net account a couple of months ago, and allowed him to put his account into his own. Reading what you posted there, it seems it would have been fine to just put all 5 accounts under my B.Net.

I will tell you that the only real difference I've seen is that it's much easier to transfer toons between WoW accounts of a single B.Net account. No need for those Security Questions.