In general, virtual communities value knowledge and information as currency or social resource. What differentiates virtual communities from their physical counterparts is the extent and impact of "weak ties", which are the relationships acquaintances or strangers form to acquire information through online networks. Relationships among members in a virtual community tend to focus on information exchange about specific topics. A survey conducted by Pew Internet and The American Life Project in 2001 found those involved in entertainment, professional, and sports virtual-groups focused their activities on obtaining information.