Is there a limit on resource sharing?
It's a relatively frequent strategy in 2v2 matches in StarCraft II for one player to immediately leave the game, allowing his ally to have a very strong economy to deal with his two opponents. Of course, this still takes a lot of micromanagement for the player remaining in the game to build up his own base and his ally's economy at the same time.
It is particularly powerful with a Terran/Protoss team, because Terran can mine so quickly with MULEs and the Protoss player, given extra money, can produce such a powerful army.
Is it possible to employ this strategy without the Terran player leaving the game, however? Is there any limitation to the timing and/or amount of resources that can be shared between players? Can the Terran player start feeding the Protoss player extra resources immediately?
I don't think there's a cap on the amount of resources you can send allies. I do not have a definitive source for this but I have done some testing:
My team once tried a strategy where one of us only built expansions and economy, protected by static defenses. She then piped the resources to my friend and I, who went for high-tech builds. She never ran into a limit on sending resources. This "strategy" is kind of fun since it lets one person handle all the macro and another all the micro, but it has it's own risks.
You cannot send resources immediately though. When you start a game, if you click the transfer button right away, you will see there is a delay before you can start sending (I think it is 5 minutes but I could be wrong). I assume this is to prevent a true cheese rush where people send all their resources to one person, effectively letting one person start with 18 workers.