I don't know, this one doesn't bother me as long as it was my option to watch the videos. There's a game called Another Case Solved, where you play a detective who's basically solving minigames. At your office, the phone rings periodically, and if you pick it up, you get the choice to watch a quick video and get free currency. It's very unobtrusive, and can be helpful if I only need a couple more bucks to to buy something.
Yeah, that's a good example of it put to good effect. I think what I have more of a problem with are games that have a window pop up to say, "Hey, try this game! Install it and win free currency!" and games that have you visit a random website to earn more free currency. The videos feel rather harmless in comparison.