I've never picked up hitchhikers when alone, but when I used to drive around the country for work with 2 or 3 other guys, we'd occasionally give someone a lift. Obviously you have to make a judgement call, lots of scumbags out there. But, in our experiences it made for some interesting stories. We picked up every stranded driver that wanted a ride to the next exit with something useful. Occasionally found them rides going back to their vehicle after vouching for them to truckers. One dude we let ride with us for a few hundred miles because he just went to sleep when he got in the truck and we could tell he was just glad to sleep in a warm and safe place.