Yes, but wouldn't that be the best part about partial file transfering, its like having a file cache. Freeloaders who download popular files would also be uploading the portion they have to others. It would be impossible to freeload. The only problem with this setup is that files could be shared when nobody has the complete file(only problem with edonkey). A solution would be to reward people who share rare complete files. The ultrapeers could keep track of highly demanded files that are not complete on the network. A user could request this list and if possible add any of the files to their shares. In return the user would get higher priority in download queues or for the best sharers a reserved upload slot.