Interactive television is the biggest pipe dream.
People like to interact with information devices such as the computer or the Internet, but they don't necessarily want to interact with everything. You don't interact with a Broadway play except to laugh or applaud. Audiences used to heckle stage performers and routinely throw vegetables in 1850 theater houses, but this practice was abandoned. Today, nobody yells at performers at a Broadway musical. Even at public events where yelling and ridiculing is accepted, such as baseball and football games, there's no true interaction.