If the GM is just going to stipulate all this stuff, what is the player there for? To provide some emotional language and the odd tear?
When I play a RPG I expect to be actually making decisions that matter. I'm not just there to emote my way though events the GM decides are taking place.
Because it makes them pointless, or reveals them to have a completely different significance from what they appeared to - and in a context where the players had no control over that because the players had not choice but to take on the fetch quest (as that was the game the GM was offering).
In the specific instance of the game you left, and without knowing any more than you've told us, I'd posit from what you say here that the GM's first mistake came long before revealing or even planning for the sponsor's deception: he didn't give you options as to what your first adventure might be, when GMing a table full of players who wanted to be able to make meaningful choices.
Which, to be fair, is a frequent occurrence: finding a rationale for the party to form and get into its first adventure isn't always easy. Once things are rolling it's far easier to throw in some options to go with whatever naturally develops through the run of play and-or comes from the players.
But expanding from that to the more general idea of sponsors or mentors or patrons or any other NPC not being what they seem, I still maintain this to be a valid tool in the GM's toolbox. I also maintain that low-level adventurers in a typical RPG setting
would often be looked on as patsies by less ethical but more powerful individuals or groups:
Sponsor: "You're a bright eager bunch of just-out-of-training adventurers ready to prove yourselves to each other and to the world? Sure, yeah, we got a job for you..." <
details mission and sends party on their way>
Assistant: "Boss, didn't you just send them on a suicide run?"
Sponsor: "Yep, and we can't lose. Either they succeed and get us the McGuffin or they don't, and if they don't that's a few more down-the-road threats taken care of..."
This goes back to the contrast I have drawn upthread between a story (in the sense that films, novels etc have stories) and tactical or puzzle-solving choices.
Ah, but using film-novel stories to compare to RPG stories has some problems.
First off, a film script or novel has one controlling hand* deciding how things will turn out and what events will occur on the way to getting there. This same controlling hand can and does decide ahead of time which protagonators will survive, which if any will die, and what becomes of the villains or foes in the end. An RPG doesn't really have any of this unless its GM is heavier-handed than even I would likely put up with.
A better, though still imperfect, comparable might be to a long-running TV series where the writers don't know if this season will be the last or whether the show will get extended durng the off-season.
* - which can be one or more actual people, but the end result is the same.
With an RPG there's no way of determining who will survive and-or be involved to the end - dice are troublesome that way, and characters get cycled in and out, and players come and go - nor of determining where things will go in the story after maybe the opening chapter, i.e. first adventure. (exception is if one is running a hard-line AP, but even there the character/protagonist survival piece is still an unknown)
An RPG is by its very nature far more open-ended than any book or film, and - again unless the GM is very heavy-handed - the story that comes out of it can often only be seen in hindsight. A novel writer knows that this coming fight against the BBEG is the final showdown and that the heroes will win out; she just has to write the words to suit what she has in mind. At a game table neither the GM nor the players know how the coming fight will turn out until after it's been played through - maybe the BBEG dies, maybe he or the party runs away, maybe he even wins and captures or TPKs the party; and in any case this may or may not be the final showdown at all.
Add to this that in an RPG there's several potential "authors" sitting around the table, each of whom might have completely different ideas on where the story should go next and-or what aspects of the current story are holding their interest and what aren't. This just adds to the overall unpredictability.
Lan-"remember, kid - don't trust anyone"-efan