Consumers love you, love your place and love your food - but why are they going to share their contact information to join your loyalty program? Statistics suggest that many of your customers would join a program, if it were available (50-80% in other industries) but online loyalty programs I think are going to experience a significant slowdown if the social option is not provided. Marketing Sherpa reports that as many as 86% of consumers would ignore or leave an enrollment if that enrollment required more than a click or so (more than it takes to say 'yeah - connect using my FB credentials'). To me this is an invitation by the consumer to access and authenticate them by their Facebook log in, which I'd prefer over a standalone, not connected to the social graph kind of log in.
This permission can provide the marketer access to the social graph, and thus a network of Facebook friends that averages around 150 other prospective consumers for your restaurant. This kind of access also will matter as we see systems that can read, understand and present the consumers preferences that are gleaned from the posts, discussions and input provided by the consumer themselves. Having this kind of connection via their social persona is essentially the consumers permission to enhance the customer experience and not just delight, but elate them in their visit to your restaurant. The ability to make full use of this data is still ahead of us for sure, but if marketing Sherpa is tight (and I think they are) consumers are already expressing fatigue in the account creation and log-in process for yet another social site or coupon / deal site - what we do not want is that it be your site and your loyalty program.
The answer is a loyalty program that leverage the existing social accounts and provides the consumer access to your loyalty program in exchange for access to their social graph.