BET Network is the latest media company to form its own vertical ad network. The Viacom (NYSE: VIA) unit’s digital media group will run the ad network, which will mirror the cable channel’s focus on music, entertainment and lifestyle content related to African Americans. Since BET’s brand is so well known, the company is presenting itself as a bridge between marketers who want to better target the urban and multicultural market. The project is starting off fairly small, as BET has about 30 sites in its network. Still, BET has a number of resources within Viacom from which draw on. For instance, it should be able to benefit from Viacom’s recent ad serving and sponsorship deal with Microsoft (NSDQ: MSFT). Release