The New York Times Bits blogger Saul Hansell notes that in the world of broadcasting, PBS shuns commercials. On the web, things are different. The publicly supported, not-for-profit TV network just announced a deal for several programs to be streamed on the Hulu, including "Nova," "Wired Science," "Carrier" and "Scientific American Frontiers." Hulu will place a 30-second advertisement before each program, splitting the revenue with PBS. Andrew Russell, the senior VP who runs PBS Ventures, the network's money-making arm, said the company is trying to balance its need for revenue with its noncommercial heritage.