Who park on the double yellow lines outside my child's Infant school?! Which is on a hill, on a busy main road which is a 30mph limit (although there are frequent speeders coming down the hill).
I'm so sick of parents/carers who do this. The school, and Board of Governers, constantly send out letters telling people not to park on them due to safety. There were a number of accidents and near-misses last year. Still people do it, and block the only entrance emergency services could access if they needed to get in quickly 
So I was thinking of setting up a fake Facebook profile then posting photos of all the cars, Inc registration numbers, to kind of name and shame... It's probably a very bad idea tho...