The short answer is yes, and other social networking sites can help in multiple ways too.
First and foremost, social networking allows restaurants to engage customers well before they walk in the door. A local bistro can broadcast the night's specials via Facebook status. Foodtrucks can Tweet their current location. Bakeries can announce online the minute fresh bread is out of the oven.
Social networking platforms also allow for incredibly cheap promotion. Free drinks and special deals can be shared with loyal customers online.
Though some restaurants think give-aways cheapen their brand, there are many other options to promote online. Many restaurants choose to announce exclusive wine dinners -which they know in advance will likely sell out well ahead of time- to their loyal online followers before advertising anywhere else. It's even an effective medium for getting feedback from customers. Oftentimes the feedback may be blunt, but customers usually don't hold back when they post their opinions on Twitter or Facebook so you'll know exactly what they expect next time.
Beyond the obvious resources social networks offer, they can also give customers a "peek" into the kitchen. Many chefs are logging photos and videos of the work that goes into the restaurant every day, giving their customers another avenue of attachment to and perspective on their meals.
All of this leads to a big question-how do you get an online relationship with your customers started? There's no easy answer here, but ongoing work and attention is key. Once you've created a FB page or Twitter account for your business, you need to keep using it whenever appropriate. Where possible, let your customers know about your online presence and most importantly how it can benefit them (either with unique promotions or behind the scenes information about the restaurant). Lastly, make sure you take advantage of the 'networking' in social networking. Continue to Follow others on Twitter and add friends and colleagues on sites like Facebook and even your current host, GigaChef.com. These connections compound and multiply over time so you better get started!