Who's listening?!

So, my Site Meter tells me I'm getting my usual 3 to 4 hits daily; feedburner says I've got an average circulation of, oh, six; yet according to BlogMatrix, I've sent out 540 MB worth of podcasts this week alone, and that means I'm over the free bandwidth cap. Kee-rist! Who's doing all this downloading? I don't mind if it's actual listeners, but if it's bots? I'm gonna pay a bandwidth fee for bots? At this rate, I'll have to do a special feed for BitTorrent.