In general, I don't have to worry about it. I get at most a couple hundred downloads when I post a new track. The last song I posted on my website has had about 300 downloads over 3 or 4 weeks.
I know I have to give the tunes away if I want anyone to hear them. If I tried to hawk them on iTunes or cdbaby, I'd be lucky to get 1% of the downloads I get now. That's just the reality these days.
But there is the danger that a track could catch on. I once posted a cover of a 50's rock and roll tune that got picked up by a Japanese mp3 portal, for some reason. (I still have no idea why.) That one got over 3,000 downloads in the space of a couple of weeks. Fortunately, the plan I had at the time had enough headroom.
But hosts have tightened up their deals since then. If I ever get another "hit"... I'm fucked.
And that, my friends, is the new economy.