mechmouse: I believe any system that favours intercontinental sharing over sharing with someone in the same building is deeply flawed.
Pheace: While I do agree with the statement in general I do not believe I've seen a proper solution offered to make that happen though. Most people tend to suggest limiting it to IP which is absolutely ineffective as people would just create LANs and share worldwide same as they play many games worldwide with the LAN functions these days.
Pheace, We've done this dance before. But since we have a new audience I shall play my part.
Swapping credentials or using Team viewer to abuse SFS is a one moment of stupidity and greed. Maintaining a VPN with a complete stranger requires a prolonged attention.
Using hamachi or its ilk to create an ad-hoc LAN to bypass SFS restrictions would be obvious and detectable. The rapid change of external IP addresses, specially if it crosses tectonic boundaries, would be detected by the most basic of counter-measures. This of course assumes VALVe cares about stopping abuse, a couple of visits to the SFS Forum shows they obviously don't. But if we pretend they do, such flagrant abuses could be flagged up, automatically disable the SFS link. If its legit and due to some oddness it can be set back up and abusers caught and suspended.
You could, with only minor IT knowledge, create a permanent VPN link between to homes. However the effort required would probably mean you actually know the other person. Also one of you will have the downstream limited to the others upstream. Even then a heuristic scan of the network would most likely reveal its true nature. My own home network would probably flag as a False positive, but my home is exceptional in terms of network infrastructure.
The thing is, all the above is moot. Right now with the current SFS system, as long as there are 4 or more time zone between lender and borrower, the Library Lock is highly unlikely to stop you from playing each others games.
PEople abusing the current system don't need to use VPN's to abuse the current system, because it is massively flawed.
The people most likely to be effected by the Library lock are those living in the same house. Using the existing In home streaming protocols to do a peer to peer check will not increase abuse, it will only allow legitimate users fair use.