Disclaimer: I don't mind advertisements in general and I think they get a lot of undeserved hate, especially on HN, which I think is a bit funny since a lot of the folks here work at companies that wouldn't exist without lots of advertising.
I think it's a unique and interesting idea! I might only allow it once or twice because I think eventually the folks at the top of the cumulative score list will have just been the ones to watch the most ads, as opposed to the ones who are the best at your game. Or maybe something like you can watch an ad to keep your score but then you have to play that level again, and if you get a zero again you lose your cumulative score no matter what? Not sure how much that would change your mechanics.
It does not feel like blackmail to me especially if it's a limited-use type of thing.
I think it's a unique and interesting idea! I might only allow it once or twice because I think eventually the folks at the top of the cumulative score list will have just been the ones to watch the most ads, as opposed to the ones who are the best at your game. Or maybe something like you can watch an ad to keep your score but then you have to play that level again, and if you get a zero again you lose your cumulative score no matter what? Not sure how much that would change your mechanics.
It does not feel like blackmail to me especially if it's a limited-use type of thing.