The trust that some parents have

I could be a hideous serial killer ala Dexter Morgan. I could be the ringleader of a child smuggling ring. I could be plain weird. Yet parents of a child I have never met think it's ok to leave their child with me or better yet, have me collect their child at daycare and bring her home to play with C. I could never do that, implicitly trust someone with my child that I have never met.