What I'm wondering is whether many of the purposes of a demonstration (which I believe to be proving that a whole lot of people are willing to go to the trouble and risk of showing up) can be served by putting the demonstration anywhere. A demonstration has more impact if the people you're trying to pressure can see it in person, but that's become unlikely unless the demonstrators are willing to take large personal risks.
On the other hand, people's ability to record, prove, and broadcast a demonstration have improved a lot. The mainstream media doesn't always pick up hot news from the blogosphere, but sometimes it does. So, is it plausible that demonstrations no longer need to be physically near the people they're intended to impress?