He was a guy that gave 7% interest per week on Bitcoin you lent to him.
He used the first Bitcoin exchange to disperse the dividend. Later shut down (I lost Bitcoin not with Pirateat40 but others who used the closure to steel.)
Pirateat40 launched at a time when Bitcoin had been in a steady decline for over 6 months.
Lots of people were looking for things to do with there static Bitcoin and this "investment" was wildly popular.
It was obvious to many it was a ponzi - $50,000 bets were take to prove it.
It eventually collapsed he was charged and found guilty and I think in prison.
For more info try searching.
I'm not sure he's in prison yet. I think whatever criminal or civil proceedings he's involved in are still ongoing. But, yeah, the TL;DR is: he ran a ponzi scheme with bitcoin. It eventually unraveled, and most people lost money. Then he got caught.