That's a mail drop.
Ah, ok. Not from San Francisco. Never been there. Didn't know.
Although, I have to say that I have worked for companies that had no office anywhere at all. Just a mail drop, and all employees work out of their own houses.
I'm not saying that this is what Coinbase does, but it's worth considering that it's a possibility.
Lol. How has no one figured this out yet? I solved 'the mystery' in about 20 minutes. ( Google Earth <3 ) Here's a major hint:
Just look out the window at the buildings around them
The building with the slanted windows is One Sansome Street, and just from that I able to figure out their actual address.