<offtopic>
As far as why people are reading their own meanings into the opening question, it's partly because of the way the question is framed but really it's mostly because the OP didn't state any reason as to *why* they wants to know if anyone is multi-boxing more than 15 accounts.

I believe that for well formed communication on the internet, we should look back to Kipling's six honest men: Who, Where, How, Why, When and What. If a communication is formed such that these 6 honest men are present, there is left little room for mis-interpretation.
</offtopic>

I'm currently running 5 and will be upgrading to 10 at WotLK (2 Paladins 8 Shaman, might drop a Paladin for DK if they end up being easy & effective to tank with). I already ordered the software, and am leveling up 5 toons to transfer to new accounts, but since I don't see any good way to level 10 toons in parallel I'm not going to actually buy the new accounts until after I have them all leveled to 80. Which shouldn't take too long I hope.

15 sounds like an odd number, too many or not enough to raid. What do you do with 15 shaman?