I remember going to an arduino hack group once. When I went to introduce myself to the organiser he cut me off mid-sentence with a flat "I know who you are Lio" and a unblinking stare.
Now, in tech circle we often have people that are a bit "rough" when it comes to human interaction so I make allowances.
I think what he meant was I recognise you from Twitter or something. As far as I know we get along fine and I've had absolutely no issues with him before or after.
All the same, it freaked me the fuck out at the time. :D