Well... about the lip synch...
I have seen ayumi lip synching in the Asian Song Festival in South Korea where she performed B&G and M with a horrendous coreography...
I will not defend any sides but the AT08 lives didn't sound the same for me in... not even in the songs people says it sounds... They sure aren't very diferent, but there are smalls breath diferences and missed notes... And after all... she is not singing THAT good in this concert, actualy, her voice is awful in the my name's women and marionette ... If she really is lip-synching she should at least give that songs good vocals, cause I have seen her dancing and singing at the same time lot's better...
About lip-synching in general: You really can't say if someone is doing it or not if it isn't REALLY obvious (Britney's Gimme More).. small diferences between mouth movement and sound is not really a proof... even if you are watching it live from television, cause there's a diference of some minutes between filming and transmiting for edition... that's when they choose cameras and make sure not really bad will appears on TV... maybe the diference in video and sound in the AT05-06 live is bad editing... Pretty much all pop singes when perfoming something while dancing uses a backtrack of their own voices and sings a little louder than it... So if they can't sing something, it's harder to notice cause their voices are still heard... Madonna, Jolin and Namie uses it a lot... Beyonce too, but she uses it openly and don't mind dancing without singing sometimes... here in Brazil people said Kylie lip-synched cause she used this tatic... but it's not the same thing... she sings and her record voice is played at the same time... In DVD you can't really say anything... sound is heavily edited, so is image... They take like 3 days of performace and make one video... (The Hikaru's changing dress in budokan dvd). Someone said me M live at at07 was lip-synching, but her neck veins where all very visible... if she was not singing, she as screaming a lot to have that live body aspect
(I believe that she really sang it...). Even live is hard to say how much a people is singing live... if he/she is using a microphone, there's a away to program the sound equipment to fix the singer's voice even live...
By the way... in at05, I read somewhere that she confirmed a verse of Happy Ending was lip-synched cause she couldn't sing in the position she was...
Don't know if it's true...