I think this is a valid point. I ran an exit-node for a short while at home without thinking too much about it. The huge amount of traffic I was attracting (even within minutes of booting up) made me shut it off for the sake of personal convenience, but I don't think I will ever go back -
Use bandwidth limiting?
BandwidthRate 45 KB BandwidthBurst 95 KB
This is low, but that's all I can spare on my home ADSL, and at least it contributes something. Limit your home node and it don't attract more than you can spare. Also, you can lower it temporarily (the minimum is 20 KB) and just -HUP tor if you need to upload a big file somewhere or something like that.
So, life isn't perfect running a Tor server.
-Ben