When I walk into an agency and don't see any work on the walls, I suspect it's because their work is mediocre, and they're not really that proud of it. (And often, I'm right.) But this bit forwarded by stackingchairs is worth noting.
Although it’s not uncommon for agencies to have framed ads decorating their hallways and lobbies, we don’t have any. The reason is simple: by the time we got around to framing an ad, we would already have newer ads, and since you’re only as good as the most recent thing you’ve done, the framed ad would not represent our “best” work. And so, according to the law of infinite regression, our best work would, by definition, be impossible to display. If you want to see good work, don’t look in the hallway, look on your desk. Hopefully you’ll see some there. If not, look on a desk near you.
-From the Employee Handbook of Crispin Porter + Bogusky