The name naturally comes from the idea that some people will get a deck chair and sit in their backyards to participate. Not a bad idea, as long as it's sunny.
If I had known about this event in advance, I definitely would have participated. Now that it's eleven at night, the night before the night before, I'm not sure...
(Oh hell, I will join in. Maybe even do another Great Backyard Birdcount-style live-blog. Cause I'm crazy like that.
Besides, how can you NOT join in something called The Big Sit?)
UPDATE

My circle was wowed by the Loons and the Ravens and Osprey. Here's hoping the Golden Bird is in that list, though I'm expecting that to be something a bit more rare than anything we saw.
I didn't mention this yesterday, but the instructional Big Sit video is worth a watch:
Note the drunken birdwatching! I am not saying that I condone such behavior, but I am wondering, if you're going to go ahead and birdwatch while intoxicated, why stop at alcohol?
"OMG, I see an Alicanto! Ooh! There's a Rahonavis! Wow! And there's a Zapdos!!! I gotta get a sketch of this!"