Looks like parts of e621 are on the ACMA blacklist (Australian Internet Filter).
http://wikileaks.se/leak/acma-secret-blacklist-18-mar-2009.txt
That is supposedly a leaked list of filters, I have doubts about it though.
These posts were on the list
post #14094
post #14393
post #18894
post #19341
post #19602
post #19608
post #21723
Updated by baracudaboy