need a quick email so that you can leave that bogus blog comment on some fundie website or to gain access to a restricted newsgroup?
How many times has this happened to you? You visit a web site but registration is required, with a valid email address needed for confirmation. But maybe it's just a message board you want to read one time only, or a store you have no interest in shopping from again and from which you don't want to be saddled with a lifetime of spam. And you can't use a made-up email address because you have to confirm a link or send back a reply.
Christopher Null point you to 10 minute mail. Why didn't I think of this? I like to terrorize the weak minded and uniformed.