Originally Posted by RatatouilleStrychnine
The people who are tracked down by the products of their sperm donations may have ended up "with a kid on their doorstep", but it was not their kid. You can have unexpected genetic relations turn up on your doorstep whether you donate sperm or not.
I guess if this happened and you were CF, and they kept stalking you, you could go the same way as anyone deals with a stalker: Call the police and get a restraining order. Mind you, where I live, you can actually only get a restraining order against a former lover, which I think is ridiculous. I've got sense enough not to take lovers who turn out to be stalkers... it's the crazies whom you turn down and become obsessed that you really have to worry about!
And it's a good point that CF or not, you can end up with relatives making your life hell, and feeling obliged to deal with it because they're supposedly "family." But in my life, my family is the people I've chosen as family. I've got blood-relatives with whom I never ever speak (all of them, in fact, aside from my parents). Sharing DNA doesn't make you any closer to someone, it's the family-instituted indoctrination that does that...
One way to deal with the mentally-ill adoptee would be to insist they get medical attention. And if they refuse, but they insist that you're their "real" parent, then take that to court and get power of attorney, at which point you can have them put in treatment.