The concern has been with adverts for babysitting, which have turned out to be a method of making contact with a young person potentially for grooming purposes.
The Police followed up a particular advert, whereby the advertiser requested a meeting with the young person beforehand. Fortunately the young person had the sense to both arrange the meeting in a public place, and to take a parent with them. The advertiser failed to turn up, but had clearly been there and seen that the young person was accompanied by an adult. They subsequently tried to arrange another meeting and when the police investigated the suspect, he was found to be a registered sex offender.