>It seems to me that the people most effected by this will be people who actually want to reach you - Friends, family, work associates. They’ll have to jump through an extra hoop until they’re on your whitelist.

Fair point. In practice it has not been a problem. If I really want to get emails from them, I can always add them myself if they do not want to go through the trouble. On the flip side, If someone I know isn't willing to spend a minute once in their life to get access to me, it does send a strong signal on how much they value knowing me.