I'm playing yesterday at a place I've been ID'ed as a counter in the past. As long as I don't see a familiar face among PCs, it hasn't been a problem. All of a sudden a relief PC comes along and I recognize him as putting the cut card at 50% on me about 6 months ago (I have a long memory, too.) So, I get up and find another pit. Before long, the dealer reshuffles right after the player next to me leaves and I spread from one spot to two ($50 on each.) The eye must have tracked me over there and given them advance notice, as I didn't see anyone say anything to the dealer!