Here's a good one from the #iwasthere section. Continue to add your own concert/music memories throughout the weekend.
I toured as a roadie/merch bitch for a friend's semi-famous pop-punk band from 1999 until 2005 (I've been on spot duty since then due to work and a mortgage). I would like to point out that I am referring to pop-punk a la Screeching Weasel, Ramones, etc... not that crap that qualifies as pop punk these days - note: this will come into play later.
My last tour in 2005 had us hitting up the Knitting Factory in Hollywood. After the show, I am at my customary post behind the merch table, when this very drunk guy in his late 20s early 30s walks up to the table, and starts babbling on about "tell Joe I'm sorry for being a fanboy backstage, it's just that *band name* really inspired my band and I'm a little drunk and got carried away". Curious, I ask this guy what his band is called, fully expecting some random name that I've never heard of, but alas, a surprise was in store for me. His response: "I'm the drummer for Taking Back Sunday". Now, as any decent punk rocker can ascertain, there isn't much of a correlation between Screeching Weasel style pop-punk and taking back Sunday, which lead to the following exchange:
Me: "So, Taking Back Sunday was inspired by *band name*
Me: "Then how come you guys suck so much?
At this point, the gaggle of pop-punkers around me start laughing while drummer boy lowers his head and walks away.
He probably didn't deserve it (really, all the guy had done was play in a band I didn't happen to like), but of all the times I've thought of something clever/funny to say AFTER a conversation, this was one of the rare times that I actually put a clever/funny thought to good use