ESN products, like Social Sites and Yammer, give organizations Facebook- and Twitter-like features adapted for a workplace setting and designed to improve employee collaboration.

For example, ESN products, whether installed on-premise or delivered via the cloud, typically offer microblogging, employee profiles, activity streams, document sharing and joint editing, discussion forums, brainstorming tools and the ability to rate, review and tag content.

NewsGator developed Social Sites from the start to work only in conjunction with SharePoint, and the integration is tighter than with most other ESN products, including Yammer.

However, Microsoft, to the surprise of many experts in this market, decided to acquire Yammer instead of NewsGator, which made a bold bet when it designed Social Sites exclusively for SharePoint.

NewsGator executives have said they're confident that Social Sites will remain a successful complement to SharePoint, despite the tight integration that will eventually occur between SharePoint and Yammer.