There actually has been a study on why people seek Anonymity on the internet which I found very interesting. Although it seems one would come to some of the same conclusions logically without the Study, it nevertheless is a great read. Here is just a small sample of what was in the study.
Why Do People Seek Anonymity on the Internet?
Informing Policy and Design Ruogu Kang1 , Stephanie Brown2 , Sara Kiesler1 Human Computer Interaction Institute1 Department of Psychology2 Carnegie Mellon University 5000 Forbes Ave., Pittsburgh, PA 15213 email@example.com, firstname.lastname@example.org, email@example.com
About half of the interviewees (53%) used anonymity for illegal or malicious activities such as attacking or hacking others, or they engaged in socially undesirable activities like browsing sites depicting violence or pornography. Other socially undesirable activities included downloading files illegally, flaming others, ‘peeping’ others, or searching for others’ personal information online. The line between illegality and undesirability was sometimes fuzzy, and many whose behavior was acceptable in some situations, for example, within a discussion forum, were fearful it would be unacceptable in others, for example, at work. It was also impossible to cleanly separate “bad guys” from “good guys” in our data because many of those who reported antisocial behaviors (e.g., behaviors that are unfriendly, antagonistic, or detrimental to social order) also reported prosocial behaviors (e.g., behaviors that are altruistic, or intended to help others).
Online predators included criminals, hackers, scammers, stalkers, and malicious online vendors. Fear of identity theft and spam was the main concern of those who made online sales or purchases with credit cards or account information. Fear of stalking or harassment was a major motivation for hiding one’s identity when chatting, posting on forums, and building social networks.