To throw my proverbial two cents in (I'm lying, they're hay pennies), this is a fantastic idea - but on some level is merely the standardization of what I consider a rather casual RP affair.
For example. My trader is in the habit of asking passing trader's how the systems look. That sort of a friendly chit-chat between space truckers seems very natural to me.
'Hey Joe, how's the Omega-3 system look?'
'Great Bob. There was a pirate who's charging 3 mil near [wherever]. How's the wife?'
'Died in a smelting accident, thanks for the tip!'
[Bob and Joe are later cauterized by a Phantom who only did so because he heard Pat Benetar over their comm-chat]
I think you get my point. Thought not all traders are that friendly to one another, in my experience, that sort of thing does happen (the Phantom thing as well. Apparently they hate 'Love is a Battlefield'. But I digress.).
This idea is a fantastic one, and would serve as exactly the sort of formalized function one might expect of interstellar commerce. That said, it seems it might be a bit more work for the STC dude, but perhaps a trader could request the information and get it PMed to him directly. Thus not revealing his location - though it would still notify the pirates that said person is a trader.
But lets be honest. There are plenty of RP ways a pirate could get such information. It would serve to balance the benefit traders recieved from such an organization.
I'm done.
Morality, like art, means drawing a line someplace.
