While I don't disagree that prostitution should be legal, it's a bit more complicated than the utopia you just painted.
Drugs are not largely legal at all, they're largely illegal. In fact, they're entirely illegal, there's just a gray area when it comes to a few soft drugs (pretty much just weed now - and I believe truffles in some head shops possibly... but no longer mushrooms.) Bringing weed into the country: still technically illegal. Other drugs: very much illegal. Regarding drug law, I would suggest looking to Portugal as a closer representation to that perfect utopia.
Regarding prostitution, I don't know enough to have much of a personal opinion on whether legalisation would help.
I used to think very strongly that it would. Last year I visited (as a tourist, not as a customer) Europe's largest brothel [0], in Germany, and came away with the opinion that if people are going to pay for sex, in a legal system like this is the best way for it. And I still see the benefits, but I've also since read up a little and found out many of the girls in that brothel were still trafficked over, still have pimps, etc.
But... don't be too quick to jump to one conclusion or the other. Maybe the NL situation would be better if the entire world also legalised it? Maybe there are different ways of doing it to the way NL has done it. Etc.
It won't be perfect, but maybe it can reduce trafficking ?
EDIT: please down just downvote, explain what's wrong with my line of reasoning ?
On the other hand, their are routinely used in classified agencies for some tasks.
So maybe ,even with this error rate, we could see reduction at trafficking , at some risk of loss for freedom of profession. Maybe the benefits are big and the disadvantages are quite small(depending on error rates, etc) ? Maybe it's a worthwhile tradeoff ?
So no, it's not a worthwhile tradeoff, because it's hardly better than rolling dice.
Nothing wrong with your reasoning, many people on HN stupidly enough think that the downvote button is for when you disagree with a comment.
for some numbers ,see[1]- "With both P300 and P300-MERMER, error rate was 0 %: determinations were 100 % accurate, no false negatives or false positives; also no indeterminates. Countermeasures had no effect. Median statistical confidence for determinations was 99.9 % with P300-MERMER and 99.6 % with P300"
So maybe this could be a good starting point for something useful for trafficking prevention ?
[1]http://link.springer.com/article/10.1007/s11571-012-9230-0
My remaining question is how we draw the line between voluntary illegal immigration and human trafficking for this class of work. I'd guess from my perspective even the voluntary immigration would seem beyond harrowing and carries risk of abuse and death along the way, so it would be easy to paint all of it as bad, yet clearly many think this is the best chance for them and their families.