Corporate tagline -- "Build and engage your professional network."
Real-world metaphor -- Joining a professional association.
Ultimate value -- High. LinkedIn doesn't raise your value in the job market, but it automates staying in touch with your professional network.
Trust factor -- High. LinkedIn encourages people to only accept invitations to link from people you have worked with.
Reputational (idiot factor) -- Low. Concern about professional reputation tends to keep comments business appropriate.
Corporate tagline -- "Keep up with friends."
Real-world metaphor -- Hanging out with friends at a coffee shop.
Ultimate value -- Medium. Automates staying in touch with your personal network.
Trust factor -- Medium. Facebook's business success seems to rely on reducing individual privacy, beyond the natural impact of the technology itself.
Reputational (idiot factor) -- Medium. Without the conventions of the corporate world, people are much more likely to share personal opinions and trivia.
Corporate tagline -- "Find out what's happening, right now."
Real-world metaphor -- Hanging out with strangers at a bar.
Ultimate value -- Questionable. Twitter has high value for coordinating street demonstrations, celebrity branding and crowdsourcing the news in real time.
Trust factor -- Medium. You choose who to follow on Twitter, and people can block people who abuse you from following you. But Twitter's structure lends itself to getting hacked more than other platforms.
Reputational (idiot factor) -- Very high. Twitter can short-circuit impulse control and lower inhibitions. Congressmen expose themselves. Otherwise prudent adults verbally abuse public figures in the news.