The previous iteration of the agreement suggested that "You will not use our copyrights or trademarks (including Facebook, the Facebook and F Logos, FB, Face, Poke, Wall and 32665), or any confusingly similar marks, without our written permission." However, the new agreement has amended that slightly, dropping the reference to 32665 and adding in the mention of books:
"You will not use our copyrights or trademarks (including Facebook, the Facebook and F Logos, FB, Face, Poke, Book and Wall), or any confusingly similar marks, except as expressly permitted by our Brand Usage Guidelines or with our prior written permission."
32665 is Facebook's mobile texts service, using SMS messaging to update your status on the social network. It's unclear why Facebook opted to remove it from the assumed trademark section, though it's possible the company has conceded that it can't register a number.
Although Facebook has not officially registered "Book" as a trademark, the social network would obviously like to assert its rights to the term through use. That means anybody who tries to subsequently use the term for their company or site, and who also has a Facebook account, could find themselves in legal hot water, a trademark expert tells ArsTechnica. Several lawsuits have been filed recently by Facebook against firms using "Book" in what's also believed to be a land-grab for the term.