I don't think anyone is saying the renters are crazy for being cautious. Or that they are unreasonable. Just that the owner who is casually renting might not want to jump through those hoops.
Story time: I was going to help a buddy coach a summer baseball league this year. Then I found out I needed to go down to the police station, get fingerprinted, go through a whole background check, get interviewed, etc. Is it unreasonable for them to ask all that of somebody who is going to coach kids? Maybe, maybe not. But whether it reasonable or not, I didn't feel like going through it. The whole thing was just supposed to be for fun and to help out some kids.
If someone wants to make money renting points, they should get registered as a square trade seller on ebay, but up a sophisticated add, and get $15-25/point for their trouble.
Most of the folks renting for $9-12 a point on the DIS aren't in it for the money. They've got extra points, they want to get a few bucks, and want to help out the DIS community. If it's easy and fun, they'll do it. But once they have to go through a bunch of hoops to prove to a stranger that they aren't a crook, it's no longer worth it.
If somebody wants to see all sorts of proof before sending a big check to a stranger, there are many options. There are plenty of people willing to go through all that. Just understand that if you are going to treat somebody like a business, they may want to get compensated like a business.
Personally, I've rented from people on the DIS, and from VRBO many times. If the person has an established presence, has a listed phone number and address, and seems reasonable in communication, that's enough for me. Maybe I'll get burned someday. But, so far, both the outcome and the renting experience has been a pleasure.