An individual's social network has a strong impact on his or her mental and physical health. This is of particular consequence for senior citizens who are at greater risk of social isolation after retirement, due to loss of spouse, mobility issues, and recent emphasis on aging in place, i.e., in smart homes. Can online social networking sites (SNSs) such as Facebook help alleviate social isolation of aging alone by enabling seniors to maintain high-quality social interactions? How can we make senior-friendly design improvements to SNSs? A preliminary national survey (N=168) of adults over 55 revealed that for those who had joined an SNS, the primary motivation cited for signing up was persuasion by a friend or family member, while nonusers cited a strong lack of interest rather than a lack of knowledge or skill, with implications for theory and design of SNS technology for senior citizens.