I'm surprised this thread is still open considering the amount of shade and WP the mods have handed over but people will forget about this in few days, unless she does the same at the SB.
It's not that surprising. Many of the mods have a personal distaste for Beyonce and her fans.
Ok, so given the massive amount of attention she receives just based on speculation that she lip-synced, I'm gonna assume 2004 was free of all that considering there is nothing on the internet anywhere to support those claims.
So.
2004:
Live.
Being an exponentially better vocalist now than she was at that point in time, why would she choose to lip sync at the inauguration unless she had to due to the nature of the event?
http://www.youtube.com/watch?v=2tCNth-N9Z0
It seems that she sang live, with a pre-recorded backing track playing.
1:31 onwards, for a few seconds, her own vocals are the quieter ones where she weakens.