> you can own actually own the domain and the email server

I believe the worst problem here is spam. Google grew that much as email provider also because they have among the best filters out there, but what about different servers on small hosting providers? Security issues aside (I assume their sysadmins know how to setup a safe email server), I've planned that route many times and resisted because having to fiddle with constantly changing spammers lists is something I really wouldn't want to waste a minute on.