It's sometimes used in game downloaders/updaters. But some people could be potentially mad that their upload data is being used when they don't want it used. Or

It's sometimes used in game downloaders/updaters. But some people could be potentially mad that their upload data is being used when they don't want it used. Or depending on implementation, that uploading is going on in the background when they expect nothing to be happening. There might also be problems with firewalls or NAT.