E-mail addresses contain two parts: one stands before "at" sign, another appears after it. First one is usefull when we need to point to some person or service withing a domain. As far as a person has its own domain (for example, gates.com), any characters before "@" are not necessary, and we could just write to @gates.com instead of typing email@example.com or firstname.lastname@example.org.
This idea is not far from omitting "www" from the address of some site.
Assuming a domain would only ever need one email address would cause more problems than I care to think about before having the required pot of coffee. Changing the protocol worldwide would definitely save some work too huh? :)
E-mail addresses are designed for point-to-point communication. If you want to drop anything that is sent to a domain into the same mail box, then that's your choice, and easy enough to implement. But I don't think that it would be a good idea for the e-mail addressing scheme to cater to this special case explicitly.
On the positive side, RFC 2822 doesn's say anything about the form of the user part of an address, thus <*@yourdomain.com> is indeed a valid address! Assuming that your local mail software can handle it, anyway... ;)