What is the cut off for using pseudonyms on obtaining a warrant?

I assumed bitcointalk had a small member base when "altoid" joined. A quick look at their tables show 3,694 total new registered users through January 2011.

"altoid" registered on shroomery on January 27th 2011 and the "altoid" who revealed his name publicly registered on bitcointalk on January 29th 2011.