I would also suggest that a definition of prositution is very difficult in a society where many social arrangements involve the implied exchange of sex for some form of financial support. At one extreme it could be argued that a marriage involving one partner being the sole earner is a form of prostitution - indeed many feminists have made the point. Now you may very well argue that marriage is a social institution to recognise a wider relationship than purely a sexual one. So what about the mistress of a wealthy man who sets her up with home and supports her financially and "keeps her sweet" with gifts of jewllery say. Is she any less of a prostitute than the escort who accompanies her client to a meal and followed by a sexual encounter. Is it different if that sexual encounter is an explicit part of the arrangement or a voluntary extension?
If there is an element of consent or mutual attraction as those interactions, are they qualatively different from a girl being lured from eastern Europe and then forced to work in a brothel under threat of violence to her or her family in her home country? I would suggest that there is but the exact definition is difficult to identify. Is it OK for the rich or attractive to pay for sex as a convenience but not for those who might not otherwise be able to find company? Do we condemn the elderly or disabled for hiring a prostitute because they are not confident or too socially isolated to enter into a relationship leading to a sexual one or with a person whose looks are idealised as the most attractive in our society? What about the women, is there a difference between the street walker in her 30s who is trying to feed a family and the young student doing "escort" work to pay off the University fees and loans that the Blair government introduced?
What you have skimmed over are male protitutes. You link this in your diary above to prison rape and the selling of a man's sexual services by a more powerful one in the jail. I would suggest that that is similar to the position of the eastern European girls forced to work in brothels. Although there is commercial exploitation of their bodies, it is more to do with abuse and the exercise of power. There are many male prostitutes outside of prisons. Some service rich female clients who are using them purely for convenience so they do not have to go out to socialise, just like the businessman. Others alternatively or in addition service gay clients. The motive for the clients of the "escorts" who advertise in the various gay magazines or sites is surely to have sex with someone who has one of the stereotypically ideal bodies withing the community or sometimes to indulge in activities it is difficult to find a partner for. An example here might be the guy in his mid-50s who services clients who are into headmaster/schoolboy fantasies. That is of course not to say that there are not young and vulnerable boys who are forced into prostitution to survive or feed a drug habit.
While I think there would be unanimity that the owners and operators of brothels were force and coercion is used to exploit the workers, there surely is a case to be made that properly run "houses" could provide a safer working environment, certainly much safer than either street walking or setting up in an isolated room without the opportunity of either screening clients or having some personal security. If we accept that, what should be done about those who are streetwalking because they are unable to get work in the "houses" Should they be arrested and most likely fined and forced back on the streets to pay the fine?
At the very least we should ensure that advice, testing and counselling is freely available for sex workers. The abusive brothels I would suggest need no extra legislation in most countries. They are clearly involved in quasi-slavery and those running them should be prosecuted for kidnap, incitement to rape and imprisonment. Proper social services and hostels should reduce the need for the young and vulnerable to use prostitution to fill the funding gap tht means they do not have such help. We should be aiming to provide the sex workers with the best protection and working conditions we can alongside opportunities for alternative employment if they want to "retire".