LOL, unfortunately, I don't exactly agree with your list Melrose. Take it that I've not heard more than 50% of those performances, but whatever.
Lip-sync or not, I'm just grateful and proud of Ayu for putting a 3 hour concert... and singing songs that made me love them (SCAR! POWDER SNOW!)... and besides, every song is with her new vocals... at least she bothered to "record" new versions to lip sync (assuming that she really did)... better than syncing to the studio versions.
In any case, the only 2 performances which I've seen with my own eyes would be:
1) theme of a-nation' 03 in CDL 05-06 (TV version)
2) ANGEL'S SONG in PCDL
Simply because she mouthed the wrong word at that part of the song (and it would be impossible to make that syllable from your mouth at that kind of position... so no "benefits of doubts" here; and also I tried to defend ANGEL'S SONG, as I heard her singing a wrong part... I would try to find the video again and post it here for further clarifications)
http://www.youtube.com/watch?v=pPtwFj0cT0s
That is the link to the ANGEL'S SONG performance. I suggest watching it in high-quality to get a better view. Okay here are the iffy bits.
1:40 - See how her mouth is actually shaped weirdly? I tried it myself and I can make the "ta" sound, but it's muffled. At that time, the "ta" was very loud and projected... so unless she has power diaphragms or something... it would seem weird.
2:38 - That line is supposed to be "Watashi wa mabataki sae mo oshimu no" but at the 'watashi wa' part, you (I, rather) can hear a 'watashi ni' somewhere. I'm very unsure if it's Peco or Ayu, but Melrose told me both were actually singing 'watashi wa'. So I watched a few more times... and I kind of realized that the 'watashi wa' sounds much lighter and softer than the rest of the song. I don't really think she lip-synced then... since she missed a note (upon more hearings, the 'watashi wa' really sounds like Peco and I don't hear Ayu; maybe she's drowned by Peco's OMGPOWER diaphragms). She most likely ran out of breath and couldn't have enough time to sing the 'wa'. But I could be wrong. *shrugs*
2:47 to 2:48 - This time, the line is "Kimi wa se ni tenshi no hane o motsu". Notice her lips are more in a pout-shape rather than that weird lip shape at 1:40? I honestly do not know what on earth happened at 1:40, but I'm quite sure this line is live.
That could be a technical problem or anything like that. No one knows for sure because most of us are just watching from youtube/downloaded versions which have problems.
What I want to say is, I don't really believe that ANGEL'S SONG is lip synced. My heart really tells me to believe Ayu, and I guess I would because I have watched this performance several times... I believe her. And it's up to you whether you want to think she lip syncs. In my opinion, whether she lip syncs or not, she still has a certain honesty in her music. Though personally, I would feel hurt if she really does lip sync, cos it's just some sort of a... lie that you tell your fans?
"I'm doing a live but I lip sync a song!"... It's like I don't know. I'm a fan... and I really want to see her singing live instead of lip sync... because how do we say this... lip syncing is akin to a runner taking steriods. It's just taboo and not a very glorious act.
But at the end of the day, I would still support Ayu because I would understand, if she really did lip sync. I hope no one feels offended.