Well filtering out their own domains or big anonmailers or fakes is not that hard, so it's best if the address is not distinguishable from someone who is just r

Well filtering out their own domains or big anonmailers or fakes is not that hard, so it's best if the address is not distinguishable from someone who is just really bad at reading their mail. Of course they will then begin to make automated sign ups harder, maybe with captchas or confirmation links etc. which will also discourage real users and maybe kill this concept in the long run.