Much like real products, virtual goods derive their value both from the utility they provide and the social value associated with owning or giving them. Although virtual goods got their start on social networks in the form of virtual gifts, selling virtual goods within social games has become the dominant business model on social networks. This is because social games can support virtual goods that combine gameplay benefit with social value.
A great example of this is Farmville’s most expensive item: the Unwither Ring. This $45 virtual good is priced far higher than the $1 and $2 virtual gifts sold on many social networks due both to its rarity and the powerful benefit it provides the owner — the ring forever prevents the owner’s crops from withering due to neglect.
Games, with their goals and players' individual progress in relation to them, are able to attach real value to virtual items, in a way that other applications don't quite come near. This relates to the notion of social capital, which is largely symbolic and immaterial in all walks of life.