Fads still exist within social media (think Mafia Wars), but the sites themselves are here to stay. So it's important to learn how to use them. And the best way is to take the "quality" route.
Think about traditional media - tv, radio, newspaper, magazines - and the ads that stand out. We encounter thousands of promotional messages every day, but the ones that make it into our real life thoughts and conversations are most effective.
The same is true for social media. You don't have to send an update every day or boost your member count over 100 (or 1,000 or 10,000). Instead, send an update when it's really meaningful and go after those people who are your true fans.
While everyone else is "playing" with social media, spend more time honing your message - so when it's your turn, people will remember what you said.