As far as I know, prostitution is legally sex that occurs within the context of a commercial transaction.  So, would a professional (whether a doctor, lawyer, professor, or house painter) who has sex with his client during contracted time be technically a prostitute?

Is it illegal to hire a woman to produce a low budget porno flick if she conveniently "forgets" to turn the camera on?  (And is it illegal to hire a woman to produce a low budget porno flick when the final product is the property of the client?)

Is it illegal for a matchmaking service to charge for setting up a date that is expected to last for a certain duration of time?

Is it illegal for a matchmaker to be hired to arrange a date with herself?

Is it illegal for clients of a matchmaking service to engage in sexual intercourse after paying to have themselves introduced to one another?

Most of the situations you describe are thinly veiled cover stories of paying strictly for sex.

The bottom line is this:  if you are paying somebody for sexual gratification, then you are paying for sex - and that is against the law almost everywhere in the US.

What if you are paying a multinational corporation for sexual gratification?

Let's suppose that the main difference between "dating services" and providers is that a provider keeps the money, while people who meet each other for sex at a "dating service" pay a third party.  Wouldn't it then at least appear arbitrary and capricious to prosecute providers and their clients without also prosecuting multinational corporations that sell sexual access through their web sites?

And what if the amazon women on the moon don't eat cheese?

Let's not get too ridulous here.  Face it:  if you pay ANYBODY for sex, then you are guilty of solicitation.  If a lady ACCEPTS money (even if from your mythical corporation), then she is guilty of prostitution.

What "multinational corporation" are you postulating selling sex throught their web site?

I think any of the scenarios will come down to how solid the quid pro quo is. In most cases, it's a legal issue of intent. Were you paying $$$ with the intent to get laid? Or to actually do one of those things above. And, of course, do you have anything to back it up - i.e. porn producer, where are your other tapes? You ALWAYS forget to turn on the camera???

There are many internet dating sites that advertise themselves as places to find sex.  Then, one can only contact someone profiled there once one pays a membership fee.  Assuming these places work as advertised, it looks like paying for sex to me!  A short list would include HotMatchup, Yahoo Personals, LavaLife, Adult FriendFinder, and that's not including commercial sites for swingers and extramarital philanderers.

Imagine if a provider set up a parody of one of those dating sites, but instead of charging a membership fee of $60 for three months, she charges $500 (or more) for one day.  If Yahoo or AdultFriendFinder can profit from explicit personals (and not get prosecuted), why can't a provider charge for the Personal ad on her dating site and maintain a fiction of not charging for the sex that might proceed logically from answering such an ad?

Thanks.  The two concepts I was thinking about were (a) creating a legitimate explanation for every step of the transaction and/or (b) separating sex from a commercial context.  Since corporations like Yahoo generate revenue by selling spaces in their sex bazaars, I thought that providers could use linguistic camouflage to make themselves sound indistinguishable from commercial dating sites.

You are ignoring an important fact - even if you find a sex partner over one of these sites, she will not receive any of the money you paid for your membership.  In many (hopefully most) cases she won't get any money from you, either.  These sites are dating services, and even if their subscribers have sex when they meet that does not make the services accessories to prostitution.

Even if some of the subscribers are providers looking for paying clients, the fact remains that the dating service does not get a cut of their fee and does not aid or abet them in any way other than hosting their ad - which is the same thing they do for everyone else who uses them.

Your argument presumes that publishing an ad is the same thing as commiting prostitution.  That is not how it works.  The owner of a site which collects commissions from its advertisers would be guilty of pimping and/or pandering, but there is nothing illegal about accepting money in exchange for running an ad that doesn't actually solicit sex.

Your hypothetical $500 per day membership site crosses the line in a number of ways, the most important of which is that the provider keeps the money.  Another is the implicit assurance that the man will get to have sex once he pays the money, which would not be the case with any legitimate dating service.  

Many people think they have found loopholes to get around the prostitution laws, but they are all kidding themselves.  Paying for sex is paying for sex no matter how you do it or how cleverly you think you can explain it away.  Prosecutors are not dumb enough to be fooled by tricks like these, and neither are judges or juries.

The problem with this approach is that your explanations are not "legitimate".  Even if they SOUND legitimate to you, they are false.  A criminal act is a criminal act regardless of whether the defendant has a clever story to tell about it.  The best a strategy like this could possibly accomplish would be to plant reasonable doubt in the mind of jurors, but jurors aren't as dumb as you seem to think they are.

Any professional as you mentioned, take advantage of clients as you mentioned, is technically a slimeball...and probably on the news eventually (hoepfully)