I like this quote made about the advantages and disadvantages of multiboxing... it should be used to explain to noobs that multiboxing does not equal instawin:

The BG isn't won because of multi-boxing teams. There is an even number of players on both side. This multi-boxer maybe able to have coordinated firepower, but he can only concentrate on one objective. That one objective regardless of whatever it is, will take 5 members to accomplish. You have an open graveyard with no defenders, one or two character can take that graveyard as oppose to 5. A flag carrier is WSG manages to outmanuever the multiboxer, then thats FIVE opposing players thats been outmanuevered instead of one. If a multi-boxer decides to defend the flag, thats 5 people out of 10 unavailable for offense.

BGs can be lost because of multi-boxer just as easily as it can be won. The multi-boxer's ability to focus is also its downfall when you need adaptive independently thinking entities per character. Regardless of the number of players in the battleground. It is still 10 characters vs. 10 characters. Or 40 characters vs. 40 characters. There is nothing unfair here. If you lost, it was due to poor strategy on your side, or great strategy on your opponents side.