Overall, the importance of the subjective norm in predicting intention to use have been mixed. In Davis (1989) original develop-ment of the TAM, he did not find support for including the construct, but additional research has found support for including subjective norms under some conditions (e.g., Taylor & Todd, 1995; Venkatesh & Davis, 2000). For example, Venkatesh and Davis found that subjec-tive norms influenced intention to use when use of a system was mandatory, but not when voluntary. For communication technolo-gies, support for subjective norms is stronger. Social constructionist researchers (e.g., Fulk, Schmitz, & Ryu, 1995) have shown use of technology within a user’s social network to predict adoption. When email, for example, was used by more people in the individual’s com-munication network, adoption rates were higher than for individuals who knew fewer people communicating by email. Campbell and Rus-so (2003) found a similar pattern in mobile phone usage.