As far as Bey's performance goes, the difference in vocal, sound quality (different mics, different acoustics etc.) and overall tone before and after Jay's verse makes it quite obvious the first half was lip synced.
She didn't by any measure sound
bad in the part that was sung live, but the difference is obvious to anybody actively listening. Especially when you consider how much Bey loves her runs and adlibs, yet during the entire first half there wasn't a single thing out of place, and they all hit in the second half when she was actually singing live.
I'm a huge Bey fan but sometimes you've just gotta be realistic. There's really no point in denying it when it's so obvious - you just look foolish.
