Facebook owns registrations in the US for:
FACEBOOK
It used to own one for THEFACEBOOK but amended it to FACEBOOK. It has applications for:
POKE
32665 (Facebook’s text message shortcode)
FBOOK
THE WALL
F (stylized)
FACEBOOK INSIGHTS
FANSUMER
FACEBOOK PAGES
FACEBOOK BEACON
FACEBOOK ADS
BEACON
SOCIALADS
SOCIAL ADS