The people you meet at playgroup are there because they too have small children, those at work are there because of their work, those at church because of their membership, neighbours because they live there.
When you post on the internet, even on this social site for the over-50s, that you have small children and would like to know substitute grandparents for them, you are saying it to an unfiltered audience of thousands.
Those who reply to you are self-selecting. I don't know the %age of the population with leanings towards child abuse, but say 99.9% of them will be grandparents who don't see enough of their own grandchildren, or people who have not been blessed with grandchildren but wish they had been. The other 0 .1% could be replying for ulterior motives - which might not even be evident to them, until they meet the children and find out their secret desires.
Out of, say, ten thousand people reading the posts on Gransnet, 0.1% would be ten people. So it is possible that ten dodgy people will be aware that you are open to being approached. One of them could live in your area, and contact you. They won't be shifty-eyed and wearing a dirtyy mac, they will be friendly and outgoing and perfectly normal.
Just like the scoutmaster, in fact, or the music teacher who is willing to give home lessons (while you get on with the housework in another room) or the nuns or the brothers at the convent school. Trusted by all!
Crying over sad songs on the radio
I hope the new PM is kind to Larry the Cat

