My school, presumably because every student has received a student-laptop, unblocked imgur, deviantart, steam, and battlenet (among several other things).
Blockland forums has never been blocked, and the last time i was called into the office for something related to an incident with my computer, the junior grade manager told me that he was pretty sure that if he used some program that i forgot the name of, that he would see a bunch of student-issued computers using a vpn. They just don't care enough to do anything about it, I guess. lol