I used to do this too, but it's a considerable amount of effort, and doesn't really prevent much: many domain hoarders/resellers know the trick, so they'll try

I used to do this too, but it's a considerable amount of effort, and doesn't really prevent much: many domain hoarders/resellers know the trick, so they'll try to match other data they get from you, and sometimes build a fuller "profile" on you than they would if you only had gmail/other generic domain (eg if they have your name, which often leaks along email, they'll try your first name, first name + last name, initial + last name, first name + last initial, etc).