Sure Ashton Kutcher got to a million first, but his method was less than optimal (the real incentive was to wait until 999,999 people were following and then hit the button … which could have been forever). So what would have worked better? Cheap Talk has some thoughts:
A better mechanism is the following. Set a deadline, say midnight. If at midnight there are fewer than 1,000,000 followers then each of the existing followers wins a prize and the prize that the nth follower wins is decreasing in n. Thus, the 1st follower gets a larger prize than the 2nd which is larger than the 3rd, etc. On the other hand, if before midnight the number of followers reaches 1,000,000, then give only the 1,000,000th follower a prize. And it can be a very small prize.