AA: Well, that would be a logical conclusion, but I don't know whether you can just put it like that.
It seems fairly obvious that if an LP of a game is horrible, the watcher will most likely not feel enclined to play it.
However, there are probably a lot more reasons that people watch LP's than just wanting to see the LP so they don't have to buy the game.
For me, a great deal of watching LP's is because they show games I will most likely never play in my whole life, because a: I don't like playing that specific type of game or b: I don't own the console the game is for.
Along with the reasons that people watch LP's in the first place, there's also different things they expect from the LP's that they watch.
Some people like to watch tool-assisted runs, others like 'real LP's' with people talking over the game. There's people who like awesome players, and there's people who just enjoy schadenfreude and love to see people fail. I think it would be difficult, not to say impossible to make such a statement as you did.
Whew, seems like I overdid this a bit. Please don't feel like I'm trying to attack you or anything.