We are talkin DRM, of course it is crazy.
And no - the one essential thing that is missing is:
"Sure take it - I have many (to share)". You only have one share slot at any given time. That makes it more valuable. Because of that you will demand a share slot in return.
Well probably not "right now", but "sometime". The problem is, that with everyone just having one share slot open sometime from a specific person might become increasingly uncertain when it depends not only on the time another person stops lending from him, but also on the agreements he has taken to lend further games as well as if he has that game you want in your common circle.
Lending becomes something you will only do in "exchange". Probably at the same time to/from each other.
The alternative is kicking someone out from a lending slot - which results in social guilt.
edit: he/she