That's actually an interesting enough theory that I'd love to test.
My guess is that the site is generally mediocre enough that it would be hard to get more people to open their wallets except for select listing types.
If they charged to view the listings for example, I'd wager that very few people would bother and they'd lose their network effect.
My guess is that they're getting about as much money as they can without offending too many people as preservation of their user network is highest priority, as it is what allows them to keep charging money for the few things they charge for currently.
Just by putting un-offsensive elements such as a single Adsense box on each site they should be able to generate serious additional revenue without experiencing that much of critique. With that kind of traffic and legitimate profile, the un-intrusive revenue options are endless. Just additional fees for highlighted listings, dynamic pricing for a slower decay of a posting, etc. But the beauty of Craigslist is its absolute no-frills approach and consistency over years and years. Reminds me a bit on the success of Drudge. Similarly weathering all storms by concentrating on content and simplicity to the extreme.
I was naively thinking of charging users more money to increase revenue, and while you've pointed out a few very viable ways that they could easily get more wallets open, the real gold mine is likely ad revenue that nobody would bat an eye at.
The targeting/CPM would likely be fairly low, but by sheer volume alone, they'd rake it in I suspect.
I believe that the CPM for ads on Craigslist would be higher than it is for Reddit or Facebook. The key is that people browsing Craigslist are usually there to buy something rather than seeking free entertainment. Advertisers really value audiences who are ready to buy a product in their market.
My guess is that the site is generally mediocre enough that it would be hard to get more people to open their wallets except for select listing types.
If they charged to view the listings for example, I'd wager that very few people would bother and they'd lose their network effect.
My guess is that they're getting about as much money as they can without offending too many people as preservation of their user network is highest priority, as it is what allows them to keep charging money for the few things they charge for currently.