I normally run 10-15 km training runs. My warm-up has always been nothing more than starting very slowly- I run the first 3 km at a crawl, really. A few months ago I switched to "barefoot" running, and I've been warming up in the same way. But then I managed to injure myself (as I detailed in this question) despite having done my normal warm-up.
There are two excellent questions here about running warm-ups - one is a general question, and this one is about the intensity of the warm-up.
My question is this- does (long distance) barefoot running require a different warm-up from regular running? Did anyone here make changes to their warm-up as a result of switching to barefoot running?