A while ago I spent quite some time researching the prostitution thing, trying to make up my mind about it. I remember the UN report on global trafficking[1] being specially enlightening. The conclusions I took from it:
-Prohibition doesn't work. It just drives the prostitution underground, and as the pimps are already doing something illegal they don't mind going the extra mile, make it straightforward slavery and abuse the women so much than they are too terrified to escape. A small country (like Sweden) can offload the prostitution to nearby countries, but if all Europe were to do that the consequences would probably be really dire for a lot of women.
-Full legality increases human trafficking. As there is a lot of legal prostitution going on, it's easier to get away with the trafficking. In Europe usually takes the shape of organized crime importing awful lot of women from western Europe to Holland and Germany. Long term, it's thought to increase the well being of prostitutes, both imported and local, but we still have to grok how to do it without make it without the traffic.
-Not legal nor illegal. This is the situation in most countries, and the implementations vary wildly. In some countries the police does not intervene at all and it's a cesspool of mafias fighting for control, others make it a tourist attraction, while others haven't made it legal but don't prosecute the prostitutes. Curiously enough, this last approach is the one that gets the best results at stopping exploitative human trafficking as long as pimping is really prosecuted, don't remember anyone really explaining why. My guess is that in this situation large scale trafficking operations stand out much more, but who knows.
TL;DR; It's hard. Swedes are a tiny bit hypocrites in this one.
[1] http://www.unodc.org/unodc/en/human-trafficking/global-repor...