At the time I didn't really think anything of it as Yellowstone can have up to 3000 earthquakes in an average year. So having a hundred or so across a day or two, whilst a lot, was not anything too out of the ordinary for the area - especially as all of them were very, very low rankings.
It seems to have continued though with a 3.9 having now been recorded and slightly worrying authorities.
Guess Marc's Doomswatch Counter can carry on ticking!
Yellowstone Quakes Raise Explosion Fears (New Scientist; Tuesday 6th January 2008)