Turns out they moved to South of Market, 410 Townsend, on the street where it all started. When Macromind moved from Chicago to San Francisco, they set up shop on Townsend.
Here's an Infoworld article Google from 1991 that says clearly that Macromind was at 410 Townsend.
Macromind founder Marc Canter had the vision that the tech and art scene would fit into what was an industrial and largely forgotten part of San Francisco. Guys like Marc single-handedly start coral reefs.
Marc lives in Ohio now and blogs at http://marc.blogs.it/.
Scoble shot a picture of their new digs.
Now, of the top publications that cover the tech industry -- TechCrunch, Mashable, GigaOm, PaidContent -- are any of them based in Silicon Valley? It's really weird, I think TC was the only one, and now they're in SF. It's something like having no country music industry pubs HQ'd in Nashville or Memphis.
And they can hang out with the Twitter guys, a short walk. ">