I've picked up at least two dozen hitchhikers all across the country. Most of them are fellow road trippers, thankful for a ride in this age of "stranger danger" and rampant paranoia. Yes, there are very few "normal" hitchhikers; the practice does not appeal to our culture of instant gratification.
There are morose old road warriors, moving out of necessity through dreary little towns, hardly saying a word.
There are bright and cheery adventurers, thru-hikers and travelers, who will often try to pay for gas or contribute in some other way.
There are natural hustlers who offer to gas jug, panhandle, and spange your way across the country. And entitled brats who treat you like a chauffeur. In all likelihood, they will try to push you a little, see what they can get out of you. Not a big deal. Draw a firm line, it is your vehicle and your rules. I get frustrated by their freeloading, entitled lifestyle, but they are not dangerous.
And then, the all-American obsession, the unicorn of criminals: the psycho hitchhiker. Clearly, the best way to victimize people would be to stand out in the weather for hours, looking kinda rough, and hold out your thumb, knowing automatically that you will draw the attention of police officers, and that a huge portion of the population has decided never to even consider giving you a ride.
I'm not saying you should pick up hitchhikers if you feel uncomfortable with the whole concept. Too many in our society don't have the discretion and common sense God gave a billy goat. They have no idea that the donuts and soda they just bought at the truck stop are more likely to kill them than the scruffy dude with the cardboard sign saying "Tucson". Go on through life with your blinds closed, doors locked, and mind closed.
Personally, I'd rather pick up the psycho hitchhiker than let him get picked up by some old hippie mama with a big heart. Same goes for the guy flagging me down at midnight for his broken down car on the roadside that needed a jump start. It's not about taking unknown risks and "hoping for the best"; it's about reading a situation and acting instinctively according to a fixed, black-and-white code of conduct. Hitchhikers may not like me but they trust me.
</rant>