HBO: Game of Thrones Piracy is a Compliment, Doesn’t Hurt Sales
torrentfreak.com
torrentfreak.com
When the season ends, HBO would rather you buy the DVD / Bluray, since the sale of those discs pays them much more than Netflix or Hulu would.
It's certainly possible that one of the digital vendors could offer HBO enough money to change their mind there, but it's a fairly daunting check to write.
HBO has already stated that the only thing holding back HBO Go is that its current contracts with cable and satellite providers are still too profitable to cannabalize with a dedicated online offering (and more to the point, are effectively cost-free since HBO does not have to employ a sales/marketing force).
I think the problem is sports. If sports could move to online streaming, then the entire cable industry would crumble.