"The ones who love us best
Are the ones we lay to rest
And visit their graves on holidays at best
The ones who love us least
Are the ones we'll die to please
If it's any consolation, I don't begin to understand it."
...which is to say, it's all about controlling the quality to make sure it never gets high enough that folks are getting something free that they could be conned into paying for.
Online personals are big business. It used to work like this:
In any case, anyone you responded to could respond back to you.
Now it's different: Generally, you can only contact someone if they're a paid member, too. OK, well, I suppose that makes some kind of sense: Self selection of the "serious", and all that rubbish.
Except, if that were the real goal, you'd provide some kind of an indicator that said "this person can't respond to your messages". Except, you can't do that, because then the potential subscriber would realize that they were looking at a pool of potential mates that was actually quite a bit smaller than they thought.
In other words, it's a swindle -- a bait and switch. You can join for free, and post a profile, but all you're doing is providing the company with more bait. No one who sees your profile can talk to you, even if they paid for the service.
Now, this is clearly bad usability design, and bad customer service. After all, people think they're buying one thing (access to all these attractive people), and what they're actually buying is another, lesser thing (access to some unspecified subset of these attractive people).
Of course, it's all legal, because they don't lie to you: Somewhere on their site, you can bet, there's a FAQ or a short paragraph that says this is how it works. But they don't go out of their way to tell you the truth, either; with a relatively simple change to the UI, like a green-dot or a red-dot next to a profile, you'd be able to tell whether your messages to this Other of your Dreams was going into their inbox or into a black hole.
The bottom line is that businesses like Yahoo and Match and AOL do their calculations and make their bets -- and by now, those formulae have gotten pretty good. They pretty much know how many people are going to get fooled, and take the bait, and how many people are going to see through it and get pissed off enough to quit. And, more important, how many people are going to see through, get pissed -- and take the bait, anyway.
The 'net was supposed to empower everybody to participate in a global conversation about what was being bought and sold -- what "they" (really, their companies) were buying and selling. In the process of all that irrational exhuberance, a few things got forgotten: Money can still buy power; somebody else always owns the physical plant, or can get to; all else being equal (or inferior), big is still better.
And you can still fool all of the people some of the time. And that's good enough. Or bad enough, as the case may be.