I just read an article about persuasive design by Loren Baxter. Persuasive design is about making things influential, and something the great Nathan Shedroff is very concerned about.
However, in order to do that, you need the interaction to be seamless, like avoiding those design pain points on your webpage. Have a look at this presentation by Sebastian Deterding to learn more.
In any step of usage, ask yourself: Is the felt motivation to do this bigger than the felt or expected effort to do it?
No impulse without a fitting opportunity to act, no site of action without a fitting impulse
The article also lead me to this behavior grid that shows 15 different ways that behavior can change, made by Dr. BJ Fogg:
And this Design for Intent Toolkit goes straight into my research portfolio.