With a lot of these pills there is a withdrawal syndrome. Anything that's sedating, if you stop taking it, can cause rebound insomnia. The combination of knowing you haven't taken the drug, which is a psychological effect, and the lack of a pharmacologic effect, are both sort of pushing toward a poor night of sleep.
A lot of drugs are being marketed for lifestyle, as opposed to more narrow indications. I think there is a danger that it will be sort of accepted that you need to manipulate your level of arousal, either to wake yourself up with something or put yourself to sleep with something. There are a lot of other things to do first rather than settling on long-term medication as a solution.