Well used? There were plenty of tricks and companies doing shady things with the money. When it was used within the rules, youngsters were using it to go to the movies or buy music online.

I know of some tricks from friends of friends and you can find a few newspapers articles about the bonus being used to buy playstations and other electronics or converted in cash (500€ bonus -> 300€ cash).

If there is a rule, it will be circumvented. Italy and France should think about stopping taxing young people so much, instead of wasting public money in this way.