I'm basing this post off of my previous experience watching the summer olympics online. I don't expect it will be any different this time around, but perhaps NBC will surprise me.
Two years ago, as I am now, I'm "borrowing" my sister's login and password for her paid TV subscription. Why doesn't NBC allow non-subscribers to buy online streaming access? I would pay some amount of money (maybe $30?) to get access to the online coverage and they aren't letting me. I can't think of a reason why they don't make this an option...
That is, I would pay for it if the online coverage wasn't terrible in several different ways. First, spoilers are EVERYWHERE on the website and cannot be avoided. Unless I stay up until 3am to watch an event live there's no way I can watch the event the following day without inadvertently seeing the results on the website while trying to get to the recorded stream. Sometimes the spoiler is even part of the video itself ("Watch Bode Miller win gold!")!
Second, many or most of the broadcasts online are commentator free. Even IF you know all the ins and outs of curling rules, commentators are very helpful in conveying exactly what it is that you're watching (e.g. who is the player or team being shown? What is the significance of this match in the tournament? Who are they playing next? etc.). The prime-time TV broadcasts that are heavily edited to show the most interesting bits are completely unavailable online.
Third, high profile medal events cannot be watched until the DAY AFTER the prime-time TV broadcast has occurred unless you stay up until 3am to watch it live. Not only do you then have to impossibly dodge the spoilers on the website, but also radio, TV, co-worker conversations, etc. the following day.