With the later seasons of Lost, Sky One (UK) aired the newest episodes the night after their US premiere, supposedly to cut down on Sky losing viewers to pirating.
Actually BSG was aired in the UK a few months before the USA. Season 1 started in October 2004 in UK and January 2005 in USA.
People in the USA must have pirated it loads before it was shown on TV. And yet the TV numbers were still very impressive. This is evidence that piracy doesn't affect sales/viewing figures.