I'm using the component to replicate the social network icons beneath a Contact profile. I just realized that one of the icons, LinkedIn, is missing and I have no idea why.
I suspect the answer to this is "because LinkedIn connectivity is still in Beta" but Spring 12 documentation doesn't mention that the standard Social Accounts and Contacts is different to the Visualforce component.
It just says "A new Visualforce component is available, so you can easily add the Social Accounts and Contacts viewer to your custom account, contact, and lead detail pages. You don’t need to use this component for standard account, contact, or lead pages." Likewise, the component documentation doesn't make any mention of this. As LinkedIn is very important for the business, I can't imagine not having this icon in the Contact Detail page.