For those that are wanting to get the PC version of Watch Dogs, you will require to have Uplay.
All PC versions of Watch Dogs requires Uplay. Even if you buy the game on Steam, Uplay is required to play the game. This means you need to have an account and log in in order to activate the game.
Uplay has been controversial in the past because some games required you to be online all the time. It appears Watch Dogs won’t be like that on PC. You just need to activate the game once on Uplay and then you can play it offline if you wish to.