I'll post my views on the single parent idea.
My parents broke up when I was about 10, and I have not seen my father since, so I know what it is to have both a single parent and a family. Which did I prefer? I preferred having a father, I believe it has severely affected my school progress (I am still a very good student with grades, but I am not hitting the top grade in every exam like I was when I was 8/9 years old), as well as I have had no male role model in my life to look up to while I was going through a major period of my life. Truth be told, 2 parents would be greater than 1 in my life, my mother has a boyfriend who I completely detest, so I have not had an exceedingly happy period only having 1 parent due to this. Of course, my mother isolated is a wonderful parent, if I need money, books, advice or want to go to a movie, Im sure I can rely on her to do things for me - But I have noone to play sport, play video games, have playfights with, even if I have grown up from doing those kind of things, I will never experience my first trip to the pub with a dad (Im a teetotaller, but I would like to go to one), or be able to watch a big sports match with him.
Well, I have experienced both sides, and of course I was not conceived via IVF or Artificial Insemination, but I think that there is issues with single parenting, would this change if a foursome wanted to have a child or 10 people, there are relationships like this that exist and if they wanted children due to being infertile then less people would find this acceptable, and I would agree, too many parents could be a huge problem, but people exclude minorites from such debates, when it would be good to focus on them.
Something I would be happy to be the system would be a "proper persons test" of sorts, followed by being a foster parent for a while, in the case of singles, I think data would prove that single parents have a lot more to do than couples do, especially when they have to earn and things - We should test them out before allowing them to. It's a tough subject, HBK-aholic is more right than the other posters from what I have seen, especially seeing as she has first hand experience like myself of this - And I'm sure we would both agree we have wonderful parents, I don't want to assume things or invade her privacy in any way, but I think she might be happier with 2 parents of her mothers quality rather than just 1 (again, apologies if I said something out of place there, I'm not really qualified to speak for someone), and that is also my opinion, however we can flip this and say 1 good parent is better than 2 bad ones, hell even 1 bad parent is better than 2 bad ones, so in some cases 1 parent is better.
This has deviated into quite a sensitive, but extremely good discussion, long may it continue.