I'm all for being friendly, but sometimes being real friendly is also a sign that they're up to something. I remember reading an article about a Geo Cacher who got stopped by the Secret Service for circling around the White House in a car too many times. he said the guys on bikes were real nice and friendly, talked all about him and his geocaching....until the marked car of thugs showed up and detained him.

Also, if driving a nice car was the key to getting past BP, drug smugglers would have figured this out ages ago and adopted it as SOP.