We actually have a couple of sales guys in San Francisco who work out of 795 Folsom Street. I think it's a big co-working space: https://www.google.ca/maps/@37.782368,-122.400771,3a,75y,136...

seems like it's the address used in twitter bootstrap as an example.

Some developers/companies buy "virtual addresses" where their companies can have a virtual address, receive mail, etc.

Folsom Avenue? More like Folsom Street. See the eponymous fair.

Also, this used to be Twitter HQ...

I've been torn for a while. This is one of my two fake addresses to direct junk mail toward.

The other one is "1060 West Addison Street, Chicago IL 60613"

What's funny is that this article is currently (12:54 CDT) the top result from this Google search.