1) Perverse incentives. Make your customers happy: lose them. Keep your customers hoping but unsatisfied: keep them.
On the other hand, there's a win for the dating site if there are people who met there are in good relationships and talk about how they met.
I think the innate nature of dating is such that if you want success stories your incentive is to optimize as much as possible for success and the failure rate and single population will take care of it itself
If it's worth saying, but not worth its own post, even in Discussion, it goes here.