A 'live album' as a concept in general is a bit of a strange thing, thinking about it...it can never match the physical act of being there in person, and it's bound to sound different in any case since amps and PAs produce frequencies that your iPod or home stereo can never recreate (I don't want to go too far off-topic here - I'm a hardcore music nerd so if anyone starts a thread about the technical stuff I'd anjoy reading it!).
Because of that, a recording of a live event needs to provide something 'extra' to make up for the 'being-there' aspect...taking the idea of edited 'highlights' is as good a way as any to do that, i.e. picking out the best performance of each song from the tour and putting them in setlist order. It's something that concert attendees didn't get but then they were, well, there on the day!
I can understand why some people want to post vids of particularly bad performances to highlight the fact that the vocals on any given day are not necessarily what we hear on a live CD, but I'm not sure what else that's going to prove. They're trained professional singers, but they're also human beings. Nobody is going to hit every note exactly right every time; it would be unfair to expect flawless technical accuracy (that's what vocaloid is for...).
I hope my posts here are indeed interesting and aren't annoying or upsetting anyone. I cerrtainly don't want to start an argument, and if there are any old cans of worms that have caused problems in the past, I'm afarid I've not been around long enough to know what they are!