Yellowstone reminded me of how much I hate people. It should be legal to throw people into the thermal features if they walk off the boardwalk. Also, don't block the two-lane-wide one-way road to take pictures of the bison. I've seen the bison four times already. I want to see the geyser that's about to go off, let me through.
I waited two hours for Great Fountain Geyser to erupt, and it was well worth it, even with the two or three people saying "its about to go" when it really had 20 and 40 more minutes to go. I watched 45 minutes worth of geysering, then left just before another burst of activity.