In the past marketing was all about interrupting people while watching TV, reading, or driving down the highway. People have gotten pretty good at ignoring these interruptions.
To be effective today, you need to have permission to speak to people. If you are providing them with updated useful information they can use they will want to hear from you. The trick is getting their attention long enough to get their permission. Seth Godin has some great advice on the topic.
How do you get permission from your customers?