Well I haven't seen anyone live that I remember, really. I haven't gone to BayFest in years and the lineup is getting worse and worse.... BUT I am going to Warped Tour this year (end of the month woot) and there will be tons of bands @_@ Super excited.
I've seen a lot of live videos on youtube and stuff but that is nothing compared to being there, so I prefer to ACTUALLY be there instead of just watching videos. Especially since everyone does a little improv live, and if I'm expecting to hear the track and it comes out different when I'm watching the video, I get a little bummed. Nothing compares to having the music so loud it vibrates your bones.