So in the mean time I thought I would just write this. I just read an article by Dan & Heath Chip about Killing the slogans dead in FastCompany magazine. Dan & Heath Chip are the authors of the book Made to Stick.
In the article they ask managers and leaders to fight the urge to think in clever taglines. They talk about how it is important to connect an idea with stories so move people instead of just coming up with a good tagline and expecting the tagline to get the job done. I think this very well applies to preaching, presenting and giving talks. Stories connect with people much more than clever taglines.
So to add to the 30 second rule, in order to get your point across and move people to action, have a story that they can connect with and remember even after you are done with your talk.