Do you have kids yourself? I don't want to be condescending but, this is one of those things where you have to be part of the target market to understand that the protective instinct you have over your own kids is so strong and so raw that it would be really hard to overcome inside an on-demand transactional marketplace. You will also understand that kids up to school age (toddlers) generally only trust people they'r…
When we lived in Oregon we used a sitter service that would send us one of a handful of sitters. I liked the model and my daughter is interested in something similar (with a tech twist).
I am protective of my kids but I am not a helicopter parent (my wife is). My kids are social, friendly and naturally trusting. I don't teach them to "never talk to strangers".
You're completely entitled to your own views/processes wrt childcare. Just don't assume everyone feels exactly the same.
I fully understand the main issue is trust. BUT I think that's the same issue startups like AirBnB have to tackle.