Social video-sharing app Viddy has been used by a number of artists, but now it counts some among its investors. The startup – often described as an Instagram for video – has announced that a number of celebrities have either invested in its $6m Series A financing round, or signed on as partners to promote it. They include Shakira, Jay-Z’s Roc Nation and Will Smith’s Overbook Entertainment, as well as footballer Gerard Pique, skateboarder Rob Dyrdek and – tech celebs – Skull Candy’s Jeff Kearl and Twitter co-founder Biz Stone. Viddy has more than 10m registered users, and is adding 300k more every day according to VentureBeat, despite being iPhone-only for now. Artists who’ve used Viddy for marketing purposes include DJ Shadow (Bulletin, 23-Nov-11) and T-Pain (Bulletin, 31-Jan-12).