I have yet another reason to hate treadmills. For me, they cause extra blisters. Let me explain:
As I mentioned in my "I'm Back" post, I've been running in Vibram Five Fingers KSOs for about a year and a half now, and usually I run in them without socks. Since I slowly built up my distance in the socks, my feet developed some lovely calluses in the areas where I would have gotten blisters.
However, once it started to get cold enough outside here in Minnesota, I started wearing socks (specifically Iniji toe socks). Well, apparently it takes less than a month of running in socks for calluses (or at least my calluses) to weaken enough that a measly little 5 mile run gives me blisters right on the balls of my feet. They generally go away by my next run, but I still have to hobble around for a couple days with painful feet.
In short... DAMN YOU TREADMILL!