I would love to see someone throw a tomato or something on stage after the 3.99 announcement.
I will cheerfully throw any object (animal, vegetable, mineral, or artificial) at Steve Jobs if someone buys me an MWSF or WWDC ticket.
Seriously: let's make an Official MacRumors Project out of this. What we'll do is get me a ticket and inform me in advance of what announcements are worthy of bombardment (ie: "We are switching to the MIPS processor family", "iTunes now rents Xbox 360 games for download: only $129.99", "We are here to announce the next Mac operating system: Amiga OS 4", etc), and I'll go in armed.
I will sit at the keynote, biding my time, until the conditions are matched.
There will, of course, be a recall protocol. I will check the Forum Spy and if a lot of posts are in a thread called "DON'T DO IT, STHRNCMFRTR!" then I will assume that the keynote was acceptable overall and abort my bombardment. If that thread does not receive a sufficient post count, though, or (on the other hand, a "OMG KILL THE BASTARD NOW" thread appears) I will immediately leave my seat quietly and discretely, make my way to the aisle, and then charge up toward the stage, lobbing excrement/rotten fruit/beanie babies/etc as rapidly and accurately as I can.
Disclaimer: I don't particularly care if I get arrested. Just once, I'd like to make a dent in the RDF. Without, you know, ending up like Burrell Smith.
Because Burrell probably paid his own way.