I once suggested that they should just start charging for extra characters. Like, charge a penny per character, or sell a block of 100 to be used across as many tweets as you want for 90 cents. The marginal cost to them of shipping 141 characters instead of 140 is so small as to be practically nonexistent, so it'd be more or less pure profit.

Would anyone actually buy them? I think maybe they would, as long as they were priced low enough to be impulse-buyable. For the power users who live on Twitter, it could easily be worth the time it would save them over constantly having to edit their posts to get them under the 140 character limit. It could be to Twitter what in-app purchases are to "free-to-play" games like Candy Crush -- a way to skip out of a grind.