Facebook

Facebookis a social networking website that is operated and privately owned by Facebook, Inc.
Users can create profiles with photos, lists of personal interests, contact information and other personal information, and communicate with friends and other users through private or public messages or a chat feature. Additionally, users can join networks organized by workplace, school, or college. Users can also create and join interest and fan groups, some of which are maintained by organizations as a means of advertising.^Wikipedia

Superantural and Facebook

On the show
When discussing the Trickster in episode 5.08 Changing Channels:

Dean: Ally with the Trickster.
Sam: Yeah.
Dean: A bloody, violent monster, and you wanna be Facebook friends with him? Nice, Sammy.

Supernatural

• Supernatural CW Supernatural page
• Page for Winchester Bros
• Fanpage for Supernatural Hunters' Addict
• Page for SupernaturalSeries.com
• CW Supernatural page on Facebook
• Supernatural recap on Facebook by Michael Jensen on After Elton
• Supernatural: Official Magazine on Facebook
• Supernatural Conzine on Facebook
• Facebook fanpage for Rogue Events conventions
• Facebook page for Jus In Bello (convention)
• Official Facebook group for Argentina Supernatural Convention
• Facebook page for Rising Con

Actors & Associates
In January 2010, Jared Padalecki and Jensen Ackles posted a video via the fansite Winchester Bros, confirming they are not on Facebook or on any other online social media. This was prompted by stories of fans being lured into meeting with people posing as them through Twitter.

• Fansite for Clif Kosterman
• Joe Schreiber on Facebook
• Traci Dinwiddie on Facebook
• Richard Speight Jr. on Facebook
• Misha's Minions Group on Facebook
• Facebook memorial page for Kim Manners

Fan Pages and Groups

• group petitioning for a video game based on Supernatural