This article from Mobile Marketer - a trade publication which focuses on everything mobile - got me thinking about how important it is to ensure that your message fits your medium.
For example, if you are advertising on the Internet you should use different language, font sizes, and even creative than if you are advertising on a billboard. The same goes for marketing via trade shows, radio, and mobile. (There's the issue of that teeny, tiny screen.)
Think carefully about space and tone when you are writing copy. Also, be aware of how much time people are likely to spend on your medium of choice. For example, last month, visitors to this site (that means you, dear friend) spent an average of 1:17 minutes reading my prose.
Yikes! Better get to the point - and quick!