Online social networks are able to offer free service largely due to advertising in their virtual space. Advertising thus imposes itself as one of the most important building blocks for any online social network . Facebook's main source of revenue is its online advertising business where the company currently has three 3.1 percent market share of the overall online advertising market. However, if a social networking site is perceived as being overly commercialized or infested with commercial spam it risks negative consequences. For both advertisers and the sites themselves it is thus crucial that users accept advertising as a component of the social networking sites. The financial viability of these online sites further depends on the faith that advertisers have in the effectiveness of the medium.