It does not discuss the safety concerns of dating, either online or offline. It does not discuss the cost of identity verification and other security measures. It does not discuss the revenue model at all.
Craigslist and Tinder work because it's no more risky than chatting with a stranger at a bar, assuming you're smart and invite them to meet at a public place first.
AM works [1] because it charges significant amounts of money and works very hard at background checks.
All other sites in-between fail because they want to be the 'Amazon/eBay of dating', wherein they stand up a classifieds site with profiles, refuse to charge enough money to perform background checks, and promptly turn into a lemon market populated by malicious actors who are represented as vetted and safe.
There is no mistaking what you're getting on Craigslist or Tinder for "vetted and safe". You're getting a complete stranger who you haven't seen in person yet. If that's your bag, you're set.
There is no mistaking what you're getting on AshleyMadison, either. It's what they say and they work very hard, and charge quite a lot, to ensure that you'll only meet safe and vetted people.
If you want to play the in-between market, you need to charge a lot of money for accounts and use most of that money to vet people's identity. You can charge less money than a specialist site like AM ("affairs only"), but you can't have any free users, or you'll just become a lemon market like all the rest.
It's unfortunate that AM is so focused on affairs, because their model is the only one that seems to be working as an alternative to the classified-ads approach. Safety and secrecy cost a lot more than Okcupid was ever willing to charge.
[1] Not that AM is any more successful, and in fact might be more fraudulent than the rest! e.g. https://gizmodo.com/ashley-madison-code-shows-more-women-and...