Powerful for who, spammers? I don't think it is particularly useful, but if it is for some, it will definitely need to support blocking email at the generic domain.
Another usecase. Let's say I buy a domain myname.com for personal use. I might want people to contact me directly via @myname.com without having to create an unnatural sounding address like me@myname.com. I have seen people buying @surname domains and then creating emails name@surname, which is pretty weird too.