I think, in the best case scenario, you would use a known donor so that your kid could grow up knowing his/her biological father. This has been shown to be the best choice for most children who are adopted (that they know their biological families through open adoption), and I think it makes sense that the more "unknowns" you eliminate, the better the kid will feel about it.
That said, I also think it's important to remember that teenagers are likely going to rebel and be upset about any number of choices their parent(s) make(s). I was raised in a typical heterosexual family, with my married biological mother and father. And I HATED my father in my teenage years. My parents are now in the process of getting divorced, and I'm not sure that I'll choose to continue much of a relationship with my father at all. Of course, this is a *choice* that I'm making, a choice that my children won't have, but still. There is no guarantee that a present biological father would make for a happier/better adjusted kid/adult in the end.
Because we chose to use an anonymous donor (and, honestly, I'm not sure that I would make that choice again, but it's what made the most sense to us at the time), we have done everything we can to build relationships with our kids' donor siblings (who we found via the
Donor Sibling Registry), so that they will at least have some link to that side of their genetics.
Someday I'm sure that our kids will question our decision and will feel curious about the man who gave his sperm to help us make a family. But I feel confident that everything will turn out just fine in the end.
So, no, I don't really *worry* about it exactly. But I do think about it and try to prepare myself and the kids as best I can.
Lex