The "Good" - building your brand where consumers are spending over 50% of their media time
A comScore study last October showed that only 16% of Internet users click on display ads, with 8% of users accounting for over 85% of all clicks. Does that mean no one should use display ads? Hell no. It means that display is for branding your business not trying to drive action (that is what Search ads are for). Does anyone doubt that TV/Radio/Print ads can build awareness of a brand? They typically don't drive immediate calls to a business but they do build brand awareness over time so that when a consumer has a need they evaluate that product and hopefully buy it.
Studies by comScore and others have shown that display ads, regardless of clicks, generate significant lift in site visits and both online and offline sales by those exposed to the ads. This "lift" is has been proven time after time so why do businesses think their campaign isn't working when they see a low CTR? Just like TV ads or any other offline media advertising, display is about carving out space in someone's mind so they remember you when they are ready to buy. Fortunately, display advertising is so cost-effective (low CPM) that most businesses can afford to now brand themselves online where they couldn't with expensive traditional media alternatives.