[gist]

> Facebook, for one.

So let's say in theory you could add a great deal of people as friends (thousands even) and in that case it would be quite difficult for the FBI to run that down (as they say). Besides they would have to supoena records from Facebook at a certain point if the 'friend' was not someone they could easily determine just from a picture or limited contact info.

And don't even get into 'linkedin' that is filled with more people you don't really know or care about than any service.

Most likely they will just work the other way. Someone makes a trade and they then see if they are linked to anyone in anyway at the company.