The Missouri twins' case is under investigation by the FBI, which is looking into whether fraud was committed by the adoption facilitator, Tina Johnson, who ran the Caring Heart adoption agency out of her San Diego home. Johnson reportedly brokered the twins' adoption to two couples, accepting $6,000 from Richard and Vickie Allen of California, and about $12,000 from Alan and Judith Kilshaw, a couple from Wales. (The couples found out about Johnson's services through her Web site, which has reportedly been since taken down.)

The babies lived with the Allens for two months, then returned to the birth mother, ostensibly for a few days to say goodbye. They were then handed over to the Kilshaws. And now the children's birth mother, Tranda Wecker, says she wants her babies back.

"This just highlights some of the horrors that go on," says Jane Nast, director of the American Adoption Congress, an organization that represents adoptees, birth parents and adoptive parents. "And it happens all the time. That's the thing that's most disturbing ... When there's money involved in an adoption, you can be sure there's corruption."

There are no numbers on how often incidents like this occur, but Nast and others in the field say it's become all too common -- the fallout of a business that has grown exponentially over the years with little oversight. In 1966, for example, when Nast adopted her child, she says private adoption accounted for only 10 percent of the placements. Now, public adoptions -- which are handled by agencies licensed by different states -- make up only about 20 percent of the total, according to Nast.

While the amount paid by the two sets of prospective parents in the twins' adoption is not unusual, there are no regulations stating how much a broker can charge for the adoption services, which leaves a lot of room for many adoptive parents to be bilked of their life savings, say critics. Sometimes prices can get into the six-digit range.

Adoption agencies licensed by the states have to show all of their paperwork and justify the costs to the judges overseeing the adoption cases. But private adoptions represent the wild, wild West: a field ripe for those trying to make fast cash since the parties involved -- the adoptive parents and the birth mothers -- are oftentimes highly emotional and desperate.

"There are big, huge bucks being made on the exchange of babies," says Karen Vedder, president of Concerned United Birth Parents, a national support group for birth parents, adoptive parents and adoptees. "It's like a black market. It's gotten totally out of hand and I'm just so glad that this has come up in the newspaper because this situation has been going on for too long and everybody has been turning their heads the other way."

Order "Mothers Who Think: Tales of Real-Life Parenthood" from the editors of Mothers Who Think.