Did you guys actually read the map? The dots don't represent a base interest in the cars, they represent a percentage interest ABOVE all average car searches in each geographic area. a Circle means that one of the three muscle cars has a much higher percentage search area than average. If there were 10,000 searches on average for a camry, tahoe or BMW 335 in your area and roughly 10,000 Camaro searches, that means no circle for you. That DOESN'T mean zero interest, it just mean it has an average number of searches.
Those huge circles (with 1800% increase over avg) are all happening in small, rural towns where one or two rabid fans performing a 100 searches over the course of a year on cars.com can dramatically affect the percentage. If you live in a major metropolitan area with several million other people, your searches are lost in the sea of queries. Makes perfect sense why the circles are showing up "in the desert" and not in the large cities. You guys need to take a minute to read the fine print before jumping to conclusions that this data is all crap.
BTW, if you're a data junkie, you can also use google trends to compare different search terms to gauge their popularity. Here's "2010 Camaro" vs "2010 Mustang" as an example -
http://www.google.com/trends?q=2010+...ate=ytd&sort=0
Red = Camaro, Blue = Mustang
