Today's Wall Street Journal (article not online) talks about the sad state of innovation in network television sitcoms. They're loath to alter formulas developed in the 1950s, and honed over the decades, which results in a stifling sameness across productions. For example, 67% of sitcoms on the network stations feature a living room with a couch and stairs as their main set. (The stairs provide a way for characters to enter and leave the scene while talking, by the way. This could be the basis for a drinking game, but you'd get drunk too fast.)
Now, to be fair, probably 67% of US homes include a living room with a sofa and stairs. To some degree you could also argue that sitcoms are in a rut because so many feature upright mammals who seem to always be talking to each other. C'mon, how realistic is that?