If I ever HAD to hitch-hike I would profile the driver first. It sounds bad but if it comes down to my life I will keep every stereotype in mind before choosing who i feel comfortable enough with. Never a good idea but if you have to and if you have a choice, go with the 60 year old grandmother rater than the tattooed, wife-beater wearing, beer breathed, long haired dude driving a black van with tinted windows.
However I think PICKING UP hitch-hikers on the other hand, may have gotten more dangerous because people have less excuses nowadays to be stranded. Cell phones and mobile devices have made it less likely for someone to have to resort to that. So be suspicious!