I set this subject running because, like drugs, I find my libertarian instincts at odds with society's current position and wondered how "alone" I am on the subject. What follows is based on reading, observation and thought rather than direct experience so almost certainly contains gross oversimplification and stereotypes. In other words, just my 2 cents worth.
My starting point is that what two consenting adults do with each other, for reward or not, is no business of anyone else's, except a partner to whom a contrary commitment has been made. However, this is complicated by a proper need to ensure consent and avoid exploitation plus the practical reality that prostitution appears to exist to some extent in pretty much every society, whether legal or not. In short, you cannot eliminate it so you must control it, the question is "how much?".
In Sweden using a prostitute is a criminal offence. Leaving aside my philosophical objection to intrusion into private behavior, it strikes that any hard line approach like this will drive the business underground leaving workers much more vulnerable and thus is wrong.
In Singapore they have been pragmatic: there are three small areas designated for prostitution. In these there are a mixture of brothels, bars and massage parlors where workers are checked regularly for their health and immigration status. I understand that this is all much more controlled than 30+ years ago and was partly done to reduce crime. Surely this approach is better than a hard line one. Trafficking is eliminated and workers are better protected because, if attacked, you can call the police without fear of prosecution. Also, the risk to the health of the general population through HIV/AIDS is reduced.
The aspect I find most difficult is exploitation. Compare a (possibly mythical) high class hooker earning $000's a night and enjoying the life style to a woman trafficked from Eastern Europe thinking that she was going to get a job as a waitress. The first is perfectly acceptable and the second absolutely not. What about a single mother whose child care commitments are such that she can only work odd hours. Is she being exploited by the men who meet her or the employers that don't allow flexible working or provide a creche or the society that does not provide adequate support? I do not know the answer to this. However, I am sure that an absolute ban will not stop exploitation.
The other thing which I think is a problem relates to drug users who turn to prostitution to fund their habit. I assume that such people may find it difficult to turn up for a regular shift at a brothel and so the street is the only place for them to do business. I understand the wish of residents to eliminate street walking but I wonder what happens to the workers if it is stopped completely. Again, no answer to this.
Thanks to all who have contributed.