Possible Clues:

• Walls are an important part of it
• Be looking at pages in social networking service
• Very important person tells a story to social network
• Following expert schedule wastes time on-line
• Subject of the 2010 film "The Social Network"
• Social media website
• Social media company led by Mark Zuckerberg
• Site where one's comments can generate reactions
• Alternative to Friendster or MySpace