Jill Filipovic in Al Jazeera:
Current sex workers — at least those who are active on the Internet, arguably an English-speaking, financially stable and educated sliver representing sex workers who are significantly more privileged than the average global sex worker — seem to populate the pro-decriminalization group more heavily. This is not surprising, considering the perils sex workers face when their trade is outlawed, with rapes and assaults that cannot be reported to police, abuse at the hands of police, control by pimps or organized criminal cartels, arrests and criminal records that make other work impossible, murders no one cares about. (Street sex workers, for instance, are underrepresented in mainstream media stories but account for about 20 percent of sex workers in the U.S. and face much higher levels (PDF) of extreme poverty, homelessness, desperation and substance abuse than the general population — and even the overall sex-work population — does.)
It is clear that outlawing prostitution has not worked. Legalization, it would seem, would be a solution. Regulate sex work like any other job and treat sex workers with the dignity afforded to any other worker, and you undercut the assumption on the part of some johns that they can rape, abuse and rob, and you empower sex workers to go to the police without fear of arrest. In theory, legalization would even cut down on human trafficking and coercive practices. Regulation would make it easier to identify those who are in the trade voluntarily versus those who are not. Taking sex work out of the shadows would cast more light on those people who are being abused.
More here. Also see Aziza Ahmed in Foreign Policy:
Abolitionists typically insist that criminalization is imperative. Some have pushed for making the sale of sex illegal. Others, however, including feminists who oppose prostitution, support a different model: outlawing only the purchase of sex. They argue that criminalizing clients will force the sex industry out of business, liberating sex workers but not treating them as criminals.
Already, this model has achieved legislative success. Sweden outlawed buying sex in 1999; Norway and Iceland later followed suit. France is on the verge of joining the club, and a debate on the issue is even gaining steam in Germany. Feminist Kathleen Barry, author of Female Sexual Slavery and co-founder of the Coalition Against Trafficking in Women, has even called for an international treaty that would mandate “arresting, jailing and fining johns.” (She first introduced the idea in the early 1990s, but has recently revived it.)
In reality, there is no convincing evidence that punishing “johns” decreases the incidence of commercial sex. Troublingly, Sweden's sex workers report that criminalization has simply driven the sex industry underground, with dangerous consequences: Clients have more power to say when and where they want to have sex, inhibiting workers' ability to protect themselves if need be.