A billboard tries to sell you something. So does a used car salesman. But no matter how smooth the pitch, you’re quite aware of the profit motive, and you can walk away at any time.A billboard tries to sell you something. So does a used car salesman. But no matter how smooth the pitch, you’re quite aware of the profit motive, and you can walk away at any time.Consumer & Gadgets[#item_full_content]