45 out of Rock Band's 58 tracks have already been shown to the public, but a keen pair of eyes uncovered seven more previously unannounced songs in 1UP's video preview (also part of last Friday's 1UP show). However, this isn't a flagrant foul or some intentional penalty, but most likely just an oversight that ends up benefiting the gamers.
The song list shows up at 1:27, and shows the songs categorized by difficulty. Read the full artcle, or read below to see the seven "new to us" tracks, which brings the number of known songs up to 52:
The Konks' "29 Fingers"
Flyleaf's "I'm So Sick"
The Mother Hips' "Time We Had"
Anarchy Club's "Blood Doll"
The Acro-bat's "Day Late, Dollar Short"
Crooked X's "Nightmare"