There’s plenty of buzz today following Apple’s unexpected announcement of OS X Mountain Lion. Most of the attention is being focused on the numerous iOS features that are being incorporated into the new operating system – Reminders, Notes, Messages, Twitter integration and the Notification Center.

One feature that’s getting less attention is the Share Sheets feature. Share Sheets is a system-wide feature that integrates with a variety of apps – Apple’s own apps, as well as third party apps – to give users an easy way to share content. The share button in Safari, for example, allows users to post links to Twitter, to attach them to an email, or to send them via Messages. Photo Booth’s share button also includes email, Twitter, and Messages options, and adds several other services, too. Photos and videos can be shared to Flickr and Vimeo.

While sharing via Flickr and Vimeo (and Twitter) is certainly a welcome addition, there are a few services that are conspicuous by their absence. Share Sheets does not appear to let users upload to YouTube, for example. Of course, YouTube is owned by Google, so maybe its absence isn’t all that mysterious after all. Either way, it will be interesting to see whether other photo and video hosting services are added to Mountain Lion at a later date.

Also notably absent from Mountain Lion is integration with other social media services. Of course, Twitter integration comes over from iOS, but what about Facebook? There were hints last month that Facebook integration might be coming to iOS 5.1. The lack of Facebook in Mountain Lion may suggest that that may not be the case. Or it may mean that the two companies are still working toward an agreement, and that Facebook integration will be coming in a later release of Mountain Lion.

What do you think of Share Sheets? Sound off in the comments.