Spammers, trolls, and ban evaders often use temporary email addresses. PieFed now checks a list of known temporary email providers and displays a warning icon next to registrations that use such services.
If registration mode is set to "Open" (no approval needed) then the site admin(s) receive a notification instead.
A throwaway email address isn't always a bad thing but it's one factor that admins might want to take into account.
How are they meaningfully different? I just checked the list you posted above and several of the alias domains I use are on that list.
Did you think about it before implementing it?
Ah I see we are using the word alias in a different way. I was using 'Alias' as technical term with a very specific meaning. Never mind.