Nothing. And prostitution SHOULD by all means be legal.
You own your body, you do whatever the fuck you want with it. If you choose to provide a service for money with it, namely sex, I really don't see a problem. Because it's a LOT worse when your body doesn't ultimately belong to you. Who the fuck are the government, or anyone, to tell what you can or can't do with your body? They can advise, sure. But not force you to.
Now apparent criminal activities where people are forced into this kind of lifestyle is a problem. And, of course, just like with drugs, it's ONLY LIKE THAT BECAUSE IT'S ILLEGAL. Prostitution has always existed in practically every society, and it will continue to do so. But there's a difference between a bordello with stationed security, safe rooms, frequent medical check-ups and workers who get a paycheck, can take days off, and so on... and pimping on street corner. There's a whole world of difference.
Politicians, sadly, are to some extent required. Because they're more or less leaders, even though today that position is much less about leading and much more about stupid bullshit and breaking promises. Whether a purely anarchic society can or can't work, I don't care about arguing at this point - but for democracy, and all the benefits and bad things it brings, you need some kind of a leader. Publicly elected leader. And given the intelligence or interest of general public, to gain their vote politicians pretty much have to bullshit. So it's kinda, you know, our fault to an extent.
Soldiering, conflicts always existed between groups and when said groups are countries will millions of citizens, the size of the conflict is obviously going to be rather magnified. So you can't really get rid of that.
Marketing, it doesn't trick people out of anything.
Law enforcement or lack of it doesn't magically free anyone. I do not have much love for our law enforcement and especially some of the laws they represent and their methods (Toronto G20 was a pathetic fuck up on police's side) but if you're going to have any laws, you need some kind of a deterrent to breaking them. Sure, "if you do this god will hate you!" might work for some idiots, but generally if a law isn't enforced, it pretty much doesn't exist. No matter how anarchic I may or may not be, some laws are worth being defended, at least for the time being.
Taxcollectors, that depends on your political views. I probably fit somewhere under left-wing libertarian, although I mainly focus on personal freedoms. I see nothing wrong in some social programs that are directed in a smart way, so, eh, I'm okay with some taxes. Although, of course, paying a large percentage of your paycheck to the government that isn't going to do anything beneficial to you with these money is fucking annoying... Some taxes should be voluntary, in my opinion.
So, I'm okay with every profession.