As you may or may not know, Playstation Plus arrived in Brazil a few days ago. And it appears Sony have been really nice to its Brazilian users, “selling” the PS+ 1 year membership for free.
The "offer" was not mentioned anywhere officially, and people were able to stack it. It was technically possible to get dozens of years of PS+ membership for free by getting the offer several times in a row.
The article describes the full process used by people to get free lifetime PS+ membership (valid on the Vita, PS3, and PS4), although the vulnerability is now closed