I will admit that when I first stared on ACOM I was guilty of adding just about anybody through Member Trees and not really sourcing the data aside from doing the obvious date checks that you mentioned. I'm currently going back through my tree and confirming and correcting as much as possible.
In my wandering around the forums I've noticed that a lot of people complain about others doing this without digging deeper into the source material, and quite frankly I wonder why you all waste time complaining about it.
Yes, some people, like myself originally, are going to just add whoever comes up in a Member Tree hint, and if you don't like that I would just suggesting getting over it and moving on. Is not something you'll ever be able to fix largely because most people engaging in that behavior don't care.
Others who want to get serious and educated, like myself, will learn rather quickly and "grow up" genealogically, so to speak. When those people come to you and engage you for your advice and wisdom you're time will be much better spent educating those people than trying to lead a horse, that doesn't feel like drinking, to water.