Spray on truck bed liner is great stuff. I have it inside my jeep and also had it completely undercoated with the stuff. After 11 years with this stuff on it, it still looks great, not all scratched up and what not from 11 years of muddy dogs scratching the piss out of it.
However, I agree with the bigazz truck statement. Being in the city, it just sucks to see these damn things everywhere when you know 90% of them are owned by folks with a boat or trailer that gets used once a year. Meanwhile, they waste our resources as fast as they can all in the name of being free in Amercia because they can "afford" it. Check out FUH2.com for some good laughs.
As for dogs in the back of the truck, it depends on the dog. We had a lab as a kid (I'm from the Oregon coast, not many scorching days there) that, when parked, would climb up over the cab and lay on the hood because it was warm and he could keep an eye on you better. Much like the avatar of my dog on my jeep. She doesn't do that BTW, it was just a picture.
As for my dogs, they do ride in the back of the jeep unrestrained, at least one of them. The other has followed me into store once or twice. Not a big deal in home depot, but frowned upon in a grocery store. On hot days, they stay home with a big bowl of fresh water and a 40 foot maple tree that offers lots of shade.
Riley, apparently you don't live in the rust belt or you'd embrace the bedliners as a good thing. As for heat index, yep, they raise it significantly.
And some of you obviously are forgetting the joy it brings a dog to stick his face into the wind at highways speeds. The one in my avatar lives for it and whines if the car windows don't get rolled down for her. Again, for the record, the dogs do stay at home most of the summer on errand runs due to the heat. And I've parked 1/4 mile away from my shopping location just so the dogs can be in the shade. My wife and I have decided not to shop while out and about for lack of shade before also.