I voted like 2 days ago but didn't have the time to post, LOL.
I voted live, too. There are many girls in AKB that can actually sing live and they don't need any help of any special technology to sound fine. So why would they need lip-synch?
Now, as everyone has stated, sometimes they need it, as for songs where they have to jump or something, or after they've been dancing for hours. But overall, AKB has the talent, they don't need to lip-synch.