For social sharing, Apple turns to Twitter again

Apple’s decision to unfriend Facebook has turned out to be a boon for third-party social services that are now finding their way into Apple(s AAPL) operating environments. The biggest winner of them all is Twitter. In iOS 5, Apple integrated Twitter. And just like that the company saw “sign-ups more than double and the number of tweets sent increase over 90 percent,” according to Dick Costolo, CEO of Twitter.

Well, Twitter is about to get a yet another boost, thanks to the upcoming release of the latest version of Mac OS X, called Mountain Lion. Twitter, Flickr(s YHOO) and Vimeo are some of the third-party services that will offered as part of new “share sheet” that allows you to share links, photos and videos directly from the app one is using on the Mac. (Interestingly, there is no YouTube(s GOOG) in this share sheet?) Like a photo in your iPhoto? You can share it via Twitter or upload it to Flickr or email it. See a URL, you can share that  through either email, the new iMessage for Mac or Twitter. A document can also be shared through Apple’s AirDrop sharing technology.

Twitter, however, is the one that is pretty much everywhere inside the new operating system. Just as on iOS 5, a single sign-on is all it takes to share via Twitter, regardless of the app — Safari, Preview, PhotoBooth, Quick Look and others. The twitter share sheet is no different than the sharing feature iPhone or iPad users are familiar with.

“When you use Twitter single sign-on, the Contacts app displays your contacts’ Twitter profile pictures and usernames right in their contact cards,” Apple says. In the near future, expect a notification when someone mentions you in a tweet or sends you a direct message.

I think the biggest news from my perspective is the developer API.

Developers can take advantage of the Share Sheet API to let users tweet seamlessly from their apps. With the API, developers can leverage Twitter single sign-on and Tweet Sheet, so users can tweet with comments and locations, right from within their apps.