Much like Twitter's hashtags, "Tag Channels" allow users to tag their content so it turns up in a new real-time search. However, with 650,000+ posts being published daily and the obvious risk of tag spam, Tumblr has included a sliding filter that allows you to narrow down these results based on "likes" (the site's internal favorites feature) and "reblogs". The company also claims to have developed "Built-in throttling... [that] prevents monopolization by individual blogs."
First Step to Real-Time Search
In short: Tumblr is getting into the real-time search game, allowing users to contribute to a tag channel and find others who share their interests. It's a move that makes Tumblr more public: in its early days it was a fairly closed community.
The move could pave the way for a more robust real-time search, too, and perhaps even a search API ala Twitter. Access to such a stream would provide another source of real-time data for real-time search providers like OneRiot.
Facebook Integration
Separately, Tumblr is also releasing Facebook integration: photo posts, audio posts, videos and quotes are all properly styled to post properly to Facebook pages.
The changes come after a successful July for the company: 255 million pageviews were served that month.