Torrent site serves up 1000 pirated DVDs, making $20 in the process. Only 1 out of those 1000 pirates would pay the $10 required to buy a DVD [1]. Assuming as little as 2 cents of consumer value per pirated DVD, this scenario has generated $10 more income for 'businesses' and $10 more consumer surplus.
Zynga copies a game that would have had 1000 customers otherwise. They're Zynga, so they get 1500 customers and the original creators get 100. Unfortunately, this makes the game unprofitable for the original creators and the development dollars Zynga had to spend copying the game are not offset by the 600 extra players they generated. Furthermore, this game is seen as a substitutable good- no real consumer value is generated when Coke is drunk instead of Pepsi.
(Honestly, I think consumer surplus is the intuitive reason people support file lockers and not Zynga. They're probably right.)
[1] This is the only conversion rate I've seen people give actual numbers for. Citation available if requested.