In 2009 there was a great ad encouraging employers to ‘blanquear’ their personnel, which means formalising, registering them – there was a tax moratorium enabling that without penalties. I was clearly not the only person to notice this, as it provoked some comments on blogs, etc. Here is the ad itself + a parody version (about ‘negreando’ personnel, given the current financial crisis).
On the issues this raises, see my piece on the importance of formal-informal work in Argentina and Bolivia. You can find it here if you have access to a subscription to Anthropology of Work Review.