The popularity and rapid growth of social networking sites is undeniable. However, it is hard to guarantee the success and sustainability of these sites. This study will focus on identifying the key success factors for each phase in agile iteration development for social networks. A qualitative and quantitative analysis was adopted using web analytical tools to gather and measure these success factors. A comparative study between popular and unpopular social networking was undertaken to gather realistic data. Results reveal that determinants of success for agile development phases include: goal setting, developing brand image, quality content, trust building, user-centered design, technology and client server platform, service quality, user satisfaction and stability. The successful implementation of these factors will benefit developers and users in order to achieve the success and survival of the social networking website development.