I don't post here much anymore, but I have to say.... I agree with the above poster. My dd, who will be 2 soon, has a sperm donor who never, ever saw her. We agreed while I was pregnant that he would never contact us. He made my life hell and made many threats to me that he'd use my child to make it even worse. I offered to him a chance to be responsibility-free, and he jumped at it. Actually, it took him an hour to decide, so he really thought things through.
It's been so, so difficult financially sometimes, but things ALWAYS work out. I've never received any child support (this was our agreement) and he's never been around to make us miserable. No court battles, no visitations, etc.
Let me tell you, the peace of mind is worth more than any support check I could ever receive. And knowing that my daughter has been spared a trip through the court system.... I can't even explain how valuable that is to me.
Now, I know that your friend might have to deal with a father who wants to be involved, and I think that's great if he will have the child's best interest at heart. But you know what? Having a dad who makes everyone's life miserable and who uses you to get back at your mother is worse than never knowing a father at all. I say if she has good reason to believe he's just going to "be there" so he's spared paying some child support, she should think long and hard about not having him involved at all. I think it should be a mutual decision, though, and she should only bring it up if she thinks he'd take her up on it.
I never put dd's bio dad on the birth certificate, and he's made good on his promise to leave us alone. I haven't filed for child support, and we've made it okay on our own. I do have a way to reach him if there is ever a need for medical history, etc., though. Bio dad also knows that if he comes back into the picture, he'd be coughing up a lot of back child support at the same time, so that is added incentive to keep things status quo.
Some people may think I'm horrible for giving dd's bio dad an opportunity to opt out of sharing his part of the load, but I don't feel that way. She is happy, adjusted, and loves life. When the time comes for her to ask about him, she will know the truth. It may hurt then, and she might have some issues to work through, but I think those issues will be far better than the alternative.
And you know what else? Life goes on.... I've met a wonderful man, he's a great father to his kids, and he proposed to me on our one year anniversary.