The only time I've been recognized by FAs is when I was regularly taking the same flight over and over (BOS<->LAX on UA, and MHT<->PHX on WN were the big ones), and would often get the same FAs on the flight, especially when my rotation would match theirs. Heck, on the WN flights, I pretty much always sat in seat 2F as well (and half the time, the same woman would be sitting in 2D).