Adopting into single parent households is not a trivial matter

Not as trivial as what was reported by a single parent in The Age anyway ("Single parents eligible to adopt Filipino children", 5 Nov 08, The Age Online):

the evidence showed that children adopted by single people fared just as well as children in two-parent households.

Whereas there is considerable evidence otherwise:

Gunilla Ringbäck Weitoft from Sweden's National Board for Health and Welfare in Stockholm conducted the largest study ever performed on how children are affected by single-parenting. This study, released January 25, 2003 in The Lancet was conducted over the course of a decade (during the 1990s), involving 65,085 children living with a single parent, and 921,257 living with two parents. ...   children with single parents showed increased risks of psychiatric disease, suicide or suicide attempt, injury, and addiction. After adjustment for confounding factors such as socioeconomic status and parents' addiction or mental disease, children in single-parent households were twice as likely to have psychiatric disease compared with those in two-parent households; relative risks of suicide attempt and for alcohol-related disease were also doubled. The risk of childhood narcotic abuse was increased threefold among girls and fourfold among boys living in single-parent households.

I'm not saying that they should not be adopting. Having a loving single parent is much better than being a complete orphan. But having a loving father and a loving mother is still the ideal.