In the USA, once you have reached your "full retirement age" you can choose either to continue working and defer drawing social security, in which case your benefits increase by 7% for each year deferred, or draw the benefits to which you are entitled and continue to work.  You can first retire at age 62.5yrs at reduced benefits.  If you opt for early retirement you can make up to $32,000/yr while only paying the usual ss/medicare/fica taxes, ~15%. Once you have reached your full retirement age there is no longer any penalty on your earnings, regardless of the amount.

If you are working full time and earning, say $60,000/yr, it makes no sense to file for social security.  If you are making under $32,000/yr it may make perfect sense, depending on your situation and expenses.  Given that the maximum social security benefit is only about $22,000/yr many retirees continue to work at least part time if they are able.  The benefits are supposed to be indexed for inflation.....  

As the Dutch said while fighting the Spanish: "It is not necessary to have hope in order to persevere."

That would be simply illegal in Spain, I think.

I'm sure that it still happens.  Throughout the 1980s there was a fairly well documented practice of allowing workers on the dole to do casual work on the side and no lose benefits in Andalucia.

And I'll give my consent to any government that does not deny a man a living wage-Billy Bragg