According to the National Restaurant Association's 2011 Trends Forecast, "8 out 10 restaurant operators say social media will become a more important marketing tool in the future."
Look around any restaurant. The future is right in front of us. Guests are so wired into the Web, they're actually bringing the Internet with them to dinner! How much longer will you wait to take advantage of this opportunity to engage with your guests?
It would be interesting to know what the other 20% had to say about social media. Maybe they're the ones that are actually using it now.