no end of malicious, badly behaved or spammy and unpleasant applications
For a while I thought you were describing Google's own apps. I get about 4 spams a day that use Google services in some way. Hundreds more are rejected daily by mail source rules.
When I used Usenet, I recall Chinese crime gangs sending several hundred fake store spams per day, per hundreds of topics, for at least 6 years. Too bad Google didn't give a crap then.