"For upper primary pupils, they are impressionable and may be unable to discern well enough to protect themselves," he added.
These people may be sexual predators or scammers out to cheat the sellers by making off with the products without paying.
In other cases, a group of people turned up instead of an individual to bully the child and extort money from him.
Because some kids and teens don’t fully understand the dangers of talking to strangers online, they may engage in this behavior.
If they know you disapprove, they may attempt to hide it.
Digital media experts and counsellors say that while children are more socially savvy nowadays, they need more guidance on protecting themselves both online and offline as more young people take the interactions beyond their screens.
Mr Chong said they wanted to collect data on this issue as there have been cases reported in the news about online friends who turned out to be child sex predators.In Singapore's worst case of sexual abuse of boys so far, a 31-year-old Malaysian engineer was sentenced to 30 years' jail and the maximum 24 strokes of the cane in March for sexually assaulting 31 boys, some as young as 11, whom he met online.He used different identities to befriend the boys on Facebook and tricked some of them into thinking that they had mutual friends.A poll of 2,500 upper primary and secondary school children found that a third of the older students and a tenth of the younger ones had met up with someone they had first encountered online in the past year.About a third of the students who had these meet-ups rated the encounters as slightly or very unpleasant, meaning they would think twice about meeting the person again, or not meet the person a second time as negative things had happened.Dr Carol Balhetchet, senior director for youth services at the Singapore Children's Society, said individuals sometimes turn out to be "a lot older than they said they were and they may want more than just to hold your hand".