NBC will not be offering live online feeds of any events that will be broadcast on TV. The ones broadcast on TV will, of course, include the most popular events and the ones that people are most likely to tune into. The video of the events will be on NBC's site only after the events have been completed. With this in mind, it is clear that NBC views its online offering as a supplement to their TV broadcast and not as any sort of a replacement.
Many have been really quick to heavily criticize this move by NBC, but I'm not jumping on that bandwagon just yet. I am usually not one to defend old media (see my post on Why Broadcast TV Sucks), but I have some sympathy for NBC here. I applaud NBC for taking this major leap into the online distribution of this major event in the first place. It's an unfamiliar road and a departure from a model that has worked for NBC for a very long time.