How did this happen? NBCU is making itself usable: it will not accept pre-roll online video ads longer than 15 seconds for short-form video content. The exception will be full-length episodes of broadcast-TV shows, which are longer duration and ad breaks are non-frequent. a revenue risk, considering about a quarter to a third of all pre-roll coming into NBC Universal still clocks in at 30 seconds. Not sure if other networks have similar policies, but will probably follow suit in some form soon.