Very nice idea, but you should let users tweet in the middle of the video or at the end. If you force me to tweet before I won't watch it, but in the middle I will be very likely to.
That's probably true for most people if it's just a video in the middle of a blank page, but I would guess that you can pretty easily get people to tweet to watch the video if you a) put up a compelling description of the video or series and/or testimonials, or b) already have a dedicated following.
If Seth Godin or Ramit Sethi did this, I doubt they would have any trouble at all getting thousands of tweets on each video.
If Seth Godin or Ramit Sethi did this, I doubt they would have any trouble at all getting thousands of tweets on each video.