At the Gillian Welch show in Stoughton the other night, there SEEMED to be a lot of this. Dave Rawlings on a couple songs was taking special care to finish up a song just right but we sure didn't get to hear it due to the "WOO"s and as I said, generally too eager applause.
Contrast that to when I saw Suzanne Vega there and the audience was perhaps even overly respectful in letting her finish. A couple times I was ready for her to say the song is over you can applaud now.
I had the thought that the "eagers" were going out of the way to let Welch and Rawlings know they were a big fan, and not just appreciating the music as it was played.