The last generation of Web is characterized by??social networking services where users exchange a growing amount of multimedia content.??The impact of these novel services on the underlying Web infrastructures is significantly different from traditional Web-based services and has not yet been widely studied.This paper presents a scalability and bottleneck analysis of a Web system supporting social networking services for different scenarios of user interaction patterns, amount of multimedia content and network characteristics.Our study demonstrates that for some social networking services the user interaction patterns may play a fundamental role in the definition of the bottleneck resource and must be considered in the design of systems supporting novel services.