Could it be that websites like del.icio.us and StumbleUpon generally have better sharing methods already than e-mail, which is not as quick of a method? Sites t

Could it be that websites like del.icio.us and StumbleUpon generally have better sharing methods already than e-mail, which is not as quick of a method? Sites that are dedicated to sharing generally have bookmarklets, browser toolbars, and other programs to make it easier, whereas e-mail is something that it may be easier to do with AddThis.