I kept mistyping it even when I was a semi-frequent user: del.icio.us, deli.cio.us, de.licio.us, del.ici.ous, etc. For some reason I kept doing the latter out of some sort of symmetry (3.3.3), even though obviously I know that .ous isn't a valid TLD. The even dot spacing is one reason I find cr.yp.to easier.