Mobile app builder for social media stars Victorious has launched, according to multiple media reports. The Santa Monica, California-based startup, which is still in stealth mode for the most part, plans to build standalone apps around the content of standout stars from YouTube and other social video sites. The launch is significant because the company was co-founded last year by former YouTube execs Bing Chen and Sam Rogoway, and has already signed several YouTube stars with video traffic in the millions per month.