Now there are many talks about this situation, and Tor in general, so I want to say a few words.
First, I strongly recommend to read this document:
http://scribd.com/doc/172773407/Ulbrich ... -Silk-Road
This is primary source about the incident. The rest is just retelling and speculations.
Second. The story in brief:
FBI Agents were googling Internet to find out where SilkRoad was first mentioned.
The earliest posting was found on shroomery.org (Magic Mushroms forum) dated Jan 27, 2011, from user "altoid":
I came across this website called Silk Road. It's a Tor hidden service that claims to allow you to buy and sell anything online anonimously. I'm thinking of buying off it, but wanted to see if anyone here had heard of it and could recommend it. I found it through silkroad420.wordpress.com, which, if you have a tor browser, directs you to the real site at http://tydgccykixpbu6uz.onion. Let me know what you think...
This was the only message ever posted on the Shroomery forum by "altoid", indicating that he had joined the forum
solely to post this message.
Two days later, Jan 29, 2011, somebody with the name "altoid" posted similar message on bitcointalk.org.
On Oct 11, 2011 user "altoid" on bitcointalk.org stated that he was looking for an "IT pro in the Bitcoin community" to hire in connection with "a venture backed Bitcoin startup company". The posting directed interested users to send their responses to firstname.lastname@example.org
That's it. Ross Ulbright. At gmail dot com. Linked to Google+ account with his photo and everything.
"altoid", who came up first with info about Silk Road.
That's how he became a suspect. And that's the story.
The rest is not so important. Fake ID's caught on Canada border, ip-address hardcoded in SilkRoad's scripts, question on StackOverflow & so on. Federals have been watching him 24/7 and were just collecting evidence.