I've rented out points to people who I've become friends with after meeting them through the boards, but I haven't "cold rented" to someone I didn't know personally. I don't think I'd rent to anyone from the US, again unless I knew them personally, because there are a number of difficulties in "accounting" the transaction and IMHO the risk of them cancelling last minute is greater than a Brit. I'd be a little more happy to rent to people from the UK, because we have to plan ahead a great deal more and if you have a photocopy of their flight tickets, IMHO unless there is a major problem, they are unlikely to back out. I know that either you would have a deposit ( or even a payment) and that at worst your points would go back into a "holding account" but personally if someone had a tragedy ( and the synical part of me says that any late cancelation would come with an explaination of some type of tragedy, real or not) I would try to repay them any money they had given me. I'm then left with the agg of having to cancel a booking, organise the points and use them with whatever restrictions would go on them. Potentially it's a lot of work.
I do tend to be fairly well organised , so I know if I'm likely to have spare points ( not very often LOL). As there is ALWAYS someone I know planning a trip I've been able to keep it to people I know. It's unlikely that you're going to have enough points to rent out to someone for a 2 week holiday, but as a lot of people like the idea of spending just a little time on site, it's a cheap way for them to get a top quality hotel ( if you book for them a Sunday to Thursday stay) and it's unlikely to use up too many of your points. I've also rented points out for people to stay at Vero Beach for a couple of nights, again this works well if they want a few days at the beach at a really nice resort.