We’ve been writing about social video-sharing app Viddy since last year, when the app – often labelled an Instagram-for-video – started being used by artists like Panic At The Disco (Bulletin, 20-May-11). It’s not an overnight success, then, but the last couple of months have seen startling growth for the app, and its main rival Socialcam. TheNextWeb reports that Viddy is now past the 26m users mark, with 500k more signing up every day at the moment. Analytics firm Flurry has some good data on the growth of the video-sharing app category too, suggesting that Viddy and Socialcam are on their way to presenting a viable threat to YouTube. Quite a claim. “While it cannot be concluded that mobile video apps are cannibalizing YouTube, the shift in time spent between these two platforms appears to be a signal of disruption,” blogs the company.