FIND OUT WHAT CAUSED THE FLAT IN THE FIRST PLACE!
So I ran into some guy stopped on the side of the road and asked if he needed any help. (see "don't be a douchebag"). He asked for a pump because he thought that his wasn't working. As it turns out, his pump was fine, his new tube was just leaking air for the same reason the old tube was. His rim strip had slid over and the exposed spoke hole was slicing the inside of his tube. I figured this out, and fixed it happily, but this guy had already wasted his spare tube so i gave him mine. I'm happy to help people who need it. I don't expect everyone to understand how rimstrips work. But i do think that its pretty simple logic that if something is puncturing your tire, you should investigate the cause of the puncture before repeating it.
There is no such thing as karma, but there is such a thing as being a sucker and giving an incompetent person your spare tube. I'm glad I'm not the incompetent one, but a bit embarrassed to be the sucker. Next time: No tubes for you!