The proliferation of web-based communication tools like email clients vis-a-vis Yahoo mail, Gmail, and Hotmail have led to new innovations in web-based communication. Email users benefit greatly from this technology, but lack of security of these tools can put users at risk of loss of privacy, including identity theft, corporate espionage, and computer damage. In this dissertation, I examine the reasons users choose email client sites. The study begins with description of email clients and social networking sites which are part of web-based communication tools. This description is complemented by a survey of web-based communication tools to gain an understanding of the users' selection criteria, the types of human relationship information available, and how users made their choice of these communication tools. The computational problem of users' behavior in choosing the best web-based communication tool is to determine what prompted these users in their choice and why? I presented two sets of algorithms for calculating these choice inferences and reasons, one for demographic relationship in order to determine the influence of demography in choosing the best web-based communication tools, and the other were the influence of other parameters like features, technology and peer group influence ratings. Each is then analyzed theoretically to determine how accurately they calculate the opinions of users of web-based communication tools and specifically test their choice. The findings from these studies provide new understanding of (1) why users of web-based communication tools made their choice; (2) what constitutes their inspiration in making their choice and why? [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]