In one poor Northlander's case, they were scammed out of $15,000 on Facebook Marketplace during a "single unfulfilled purchase" with many more users having lost hundreds of dollars.
"It can be hugely devastating for some people losing that kind of money."
Those scammers used any items "you could imagine" to commit fraud, Harrison said.
Other cons involved people showing "easy to fake" screenshots of bank transfers or quickly cancelling a transaction before the money actually leaves their account in order to obtain the goods for free.
"The way [Facebook Marketplace] is set up is it's an international company so you don't have the consumer protection, say, that you have purchasing from Trade Me," he said.
Police received the "odd" complaint about scams from Trade Me but the difference was it offered some consumer protection because it was a Kiwi-born site. Whereas, Facebook was founded offshore by American Mark Zuckerberg.
Harrison's advice to Marketplace users was to thoroughly check a seller's profile – many were very sophisticated.
Red flags were a lack of or vague details on a person's Facebook timeline, he said.
His advice to people was to either avoid using Facebook Marketplace or organise a meeting with a buyer or seller in public with a companion and to do cash exchanges instead.
"The easiest way to prevent yourself from being scammed is to put protections in place."
Overall, Harrison and his team had received 107 fraud complaints since January 1 compared to 37 for the same time last year based on police data.
It was a global issue being made worse by social media as scams carried out via the online media joined already existing telephone and email cons, he said.
"There are still a lot of people getting hurt and a lot of money getting lost."
