One Front Street (AKA 444 Market Street) I believe.
I hear they love people randomly stopping by.
Nope, they're in this condo building on 1 Bluxome street near AT&T park. The other address is a drop box for mail downtown. I went to both addresses to check it out.
The pictures that they have had on twitter are most definitely from a office on market Market Street.
That building right there isn't anywhere near high enough. Comparing the pictures from Brian Armstrong twitter pictures (that have since been removed.)
https://blog.coinbase.com/2014/04/15/weve-moved-to-a-new-office/
The address that is a drop box is 548 Market Street #23008, San Francisco, CA 94104 which is very close to One Front Street.
Edit:
That is their old office. This new office is "hidden" cause they don't want the community to know. That is the One Front Street (444 Market Street) address possibly.
When I went to the Bluxome street address there was a guy from Zillow real estate showing a condo. We talked about his listing and then Coinbase. He verified that they were in that building. I looked at one of the condos and they're huge. They could easly run a small office from there. Maybe they moved. My wife is a property manager for Jones Lang LaSalle. Let me see if she can locate them in a JLL building. I think One Front street is managed by JLL. I can probably get a tenant roster if I really wanted to. I also know a few people that work for Shorenstein at the Russ Building, I've met many CB Richard Ellis and Tri Commercial managers and have attended a few Boma SF parties with the wife. I'll do some digging and see what I can come up with. If they rent commercial real estate in SF I bet I can find them.
Godspeed