I never participated in /b/ but I watched it sometimes. It was like staring into the id. THAT is the fundamental issue with marketing to the /b/tards: 4chan is a digital toilet stall for graffiti, not a gallery for artwork or a bulletin board for community messages. It exists as a safe space for being vile and most advertisers want the vile stuff discouraged. This is the problem Chris Poole (and Alexis Ohanian, and Kevin Rose) face: it's easy to build a community when you're doing nothing to keep out the elements that advertisers and the greater media despise. As soon as you try to be a citizen, you discover the exact same problems that everyone else has been dealing with while you were off in the hinterlands. Google has no hinterlands and never will. They often buy them and then sell them when it gets them in trouble.
I don't think I like equating keeping out elements advertisers and the greater media despise with being a citizen. /b/ is vile, but not because it's not a good community to have brands associated with. I would not mourn 4chan's passing if it went away, but we could use more places that are indifferent to advertisers.