I would think that the maximum host limit is due to the fact that for many internet connection, the upload speed is usually MUCH slower than the download speed. Therefore, if you want to download something at 100kbs, you'll need 4 hosts that can UL at 25kbs each. So I think even if there wasn't such limit, what'll happen is that there'll be many DLers, and their download bandwidth will FAR outnumber the hosts' UL bandwidth and what'll probably happen is each host will have like 10 DLers, and they'll either queue, or each host would then only UL at much lower speeds, in the end coming up to the same thing.