Like other communication networks, the Internet is establishing and reinforcing connections between market participants. By adapting to these networks, market participants are able to obtain the power of network to create new benefits in on-line markets. In this paper, we develop three stage non-cooperative game models to analyze the community related business market in electronic commerce where network externalities are present. It is found that, regardless of its market share, individual firm in a market tends to favor a community network. The analysis also shows there exist some possibilities that these community networks can trap the market in an inferior state when better alternatives are available to yield greater social welfare.