What are the chances of hosting somebody you don't like? What are the chances of showing up to someone's couch and feeling yikes?
I imagine the odds are reduced if the people using the service are largely of a similar ilk. Similar ilk works well if the service is carefully grown over time via careful word of mouth. People tend to behave much better if you know each other through a mutual friend or acquaintance. If the service grows big enough, that invisible bond of a small community will be gone and I imagine that invisible bond is what the original poster was so fond of.
It's like that house party example - if enough people show up, that delicate balance of meeting new people by being introduced through a mutual friend and having the time to make a connection with a stranger is broken and you end up 'networking' instead of connecting, as is the case with most tech meet-ups I've attended :)
hosts will be overwhelmed with requests. many guests will be freeloaders who would be better served with airbnb.
for the site to work, the influx of new members needd to be small enough so that the community csn handle it.
word of mouth is the only way to make sure that new members can get a reference before their first trip.
It worked very much as described in that post, and didn't seem to have the problems listed in yours. The biggest problem I remember with CS, was people trying to inappropriately use it to get laid.
The real problem is the same that has been plaguing the web in general - there seems to be no more room for just doing good stuff while trying to break-even or even making a modest profit. Everything has to be a "startup" with the possibility of making its founders millionaires (or more).
I got on the internet in the early/mid 90s when the web was new & for a few years it was mostly non-commercial and ran by enthusiasts and hobbyists acting according to the hacker ethos of sharing, openness, decentralization & world improvement. You could see these principles for years even behind decidedly commercial sites such as craigslist.
It didn't last for long but that's the kind of ideology couch surfing originally started in & it's sad but unsurprising to see where it ended up in.
i should have pointed out that i am speculating.
Maybe they should host first?