5.1 includes an overhaul of social networking features in the application.
You will be able to bookmark with Facebook, Twitter, ReadItLater, Instapaper, Tumblr, and Evernote, in addition to opening the page in Safari and using email. The openfeint integration is going away for now but will likely return.
> Your favorite bookmarking choices bubble to the top of the social menu for quick access
> You can disable social menu items you do not care about
> You can enter your credentials the first time you use a service rather than in settings
> A subtle notification of a successful submission fades away rather than an alert dialog to acknowledge
The global settings for social services was revamped to only provide one option: Remove all stored credentials.
The parental controls twitter and email options were removed in favor of simply "Social Bookmarking" on/off.
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