SirNickity:
Even if you can sample that fast, how do you put test leads on a circuit that is moving at a rate that necessitates that kind of speed? Seems like the capacitance of any test lead would wreck it. Crazy stuff.
I think the answer is "active probes" (MSRP about $8,000 each for this speed, but you get a set with the scope), whatever that is. Because I can repeat what Agilent says doesn't mean I understand it.