A mysterious Facebook event set for Thursday has sparked buzz that the leading social network could be adding video to Instagram smartphone picture-sharing service. The leading social network invited the media to its headquarters in the Silicon Valley city of Menlo Park where \"a small team has been working on a big idea,\" but remained hush about what will be unveiled. Online speculation at technology news website TechCrunch and elsewhere has included the possibility that Instagram will start letting people share video snippets in a style similar to a hit Vine app launched by Twitter in January. Perpetually looping videos clips up to six seconds each can be shared using Vine or easily embedded in \"tweets\" fired off at the globally popular messaging service Twitter. Twitter in December added Instagram-style smartphone photo sharing features after the Facebook-owned service made it impossible for Internet users to integrate its images into tweets. Previously, Instagram pictures shared in messages tweeted from smartphones could be viewed unaltered at Twitter. Facebook acquired Instagram last year. The original price was pegged at $1 billion but the final value was less because of a decline in the social network\'s share price. Other speculation on the Thursday event has included talk that the social network might launch an RSS reader to lure fans of a similar service that Google is shutting down at the end of this month.