Being a scrawny female, I can't give rides to strange males. That's just not safe. I always feel bad passing the hitchhikers, but there is nothing I can do about that. I've been physically attacked by a male who broke into my old apartment, and so I will never put myself in a weird position with a stranger.
Having said that..... I have been broken down on the side of the freeway in the dark and no cell phone. Very Scary. A guy pulled over and offered to give me a ride to the next exit gas station. He was a little scary looking, but I didn't really have many choices. I mean, what do I do in that situation. He was a good Samaritan and took me to the gas station, and I was able to use their phone/phonebook to call a cab.
Bless the hearts of all the good Samaritans out there. But be careful at the same time. I generally find that people who are desperate have it written all over their face (when I give money to people who need help). If they look more shifty than desperate, that'd be a red flag for me.