Don't get rich quick

I don't know if it's something specific to the UK, but there seem to be more and more cars driving around plastered with signs proclaiming "Earn £500 per day", "Retire in 3 years", "Earn more money than you'll ever be able to spend" etc.

Thing is, they're invariably on knackered, 20 year old cars with hardly any of the lights working and driven by people who look like they only have one set of clothes. Now, I guess you could argue that they're so busy saving for that early retirement that they don't want to waste any money on a new car (or a spare set of clothes). I guess you could also argue that they're so stupid they don't realise people will look at their car and think "well, it obviously didn't work for him...".

So, is this just a UK thing, or is the entire planet littered with idiots?