A 15 year old could be working in many places - probably at least has a functional understanding of value for money based on past experiences, a 5 year old almost certainly doesn't.

Age matters

> Alcohol brand starts marketing campaign targeting 18 year olds

> Alcohol brand starts marketing campaign targeting 5 year olds

When I was 15 I spent $3,500 on a video game console, controllers, Xbox live, halo, halo map packs, etc. When I was 5 I spent $1 on gum.

It's important because the article headline is a bit clickbaity. It's true that Facebook called children "whales" but not "as young as 5", since the linked chat transcript in the article mentions a 15-year old child.

Legally there is none. Both are considered minors, not capable of giving informed consent for (in many US states) marriage, employment, military service, voting, driving, or opening a bank account independently. And it's not like Facebook deserves rebuke for exploiting 5-year-olds and a Nobel Prize for exploiting 15-year-olds. But it's also true that the content of the article doesn't support the headline.

Edit: Even the math is wrong. If they're asserting that everyone's eligible to be called a "whale" who plays Angry Birds, and that the average age of an Angry Birds player is 5, then the minimum age ("as young as") of a whale isn't 5, it's less than 5.

Could you expand on what you mean by "relevant difference?"