Yes and no. It's a sensible way to represent very large pictures, and many interesting graphs are unreasonably large. Large interactive graphs can also strain an interactive viewer more than seadragon, result in incosistent views, and require some amount of interface and filter design.

On the flipside, interactivity and animation can be very welcome, and can work well even when offline.

I've had bad luck trying to draw large graphs client-side, though I'm admittedly not an expert on optimizing such things. But once you're trying to push 10,000-node graphs to the client, browsers tend to explode. Much easier to rasterize them first and push image tiles.

I disagree, Flash and Canvas are not suitable for displaying large number of objets. Using zoomable maps is a good workaround for that.

Google Maps needs an API key, whereas Seadragon doesn't and its a simple JS file < 100ko.