I'm not really sure how to resolve this. I still have no philosophical or moral objection to any consenting adults entering into an economic exchange that involves sex. If that is the state's affair, it is difficult to imagine what isn't.
My bias is definitely that [prostitution] should be legal (as should any voluntary exchange among adults that does not involve force or fraud).
However, my enthusiasm is tempered by some counter-intuitive research that found higher rates of human trafficking into countries where prostitution is legal.
So although it makes intuitive sense (it did to me, anyway) that legalizing it would improve conditions for sex workers and reduce incentives to trafficking, what actually seems to happen is that the market gets so much bigger that it incentivizes trafficking further.
In other words, this might be where the pot analogy breaks down: there is not a pent-up market waiting for pot to be legal. Most everyone who wants to smoke pot, does.
That doesn't seem to be the case with prostitution, at least based on the LSE study cited above.
But it would be irresponsible in the extreme to be cavalier about the impact of such a policy shift on the lives of sex workers, generally, and on the young people potentially being coerced into sex work, particularly.
Clearly, the devil is the details. My sense is that the Australian system works reasonably well (though I don't know a great deal about it) whereas the Dutch system appears to be failing miserably at its stated goal of bringing the sex trade above-board and improving working conditions. The last time I strolled through the red light district in Amsterdam (summer of 2005) it was...pretty seedy. A lot of the girls I passed knocked pretty enthusiastically on their windows when they saw me, and it isn't because I'm some prize--I just looked a LOT less scummy than the average guy rolling through. Drug dealers plied pretty openly on the streets, and--most unsettlingly--it was often hard to tell whether the guys working "security" were keeping the dregs out or keeping the girls in. Based on Bindel's account, it sounds like it has only gotten worse.