https://del.icio.us/export (the social bookmarking site) currently says (if you are logged in), "We're sorry, but due to heavy load on our database we are no longer able to offer an export function. Our engineers are working on this and we will restore it as soon as possible."
I tried to email support to ask about this; the Help page (https://del.icio.us/help) says to email support at del.icio.us, but that doesn't seem to work right now.