I think they work fairly well or there wouldn't be so many of them.

The one that sticks in my mind currently is for Pedigree brand dog food, and it shows shelter dogs behind fences and has a voice over (sounds like David Duchovny) saying "I know how to sit and I know how to fetch. But what I don't know if how I ended up here . . . " It's one of those ads that tugs at my heartstrings and works just as it's supposed to--to encourage adoption of shelter dogs and make the dog food brand backing the ad look noble.