CNN has this article: Psychologists highlight pitfalls of online dating 
The abundance of profiles online also may make daters too picky and judgmental, the authors say. The sheer number of options can be overwhelming, and the ease with which people can sift through profiles -- and click on to the next one -- may lead them to "objectify" potential partners and compare them like so many pairs of shoes.
"Online dating creates a shopping mentality, and that is probably not a particularly good way to go about choosing a mate," says Harry Reis, Ph.D., one of the review's authors and a professor of psychology at the University of Rochester Medical Center, in Rochester, New York.
The shopping mindset may be efficient online, but when carried into face-to-face interactions it can make daters overly critical and discourage "fluid, spontaneous interaction" in what is already a charged and potentially awkward situation, Reis and his coauthors write.
Communicating via email or instant message before meeting in person doesn't always cure this problem. Some online communication is a good thing, the researchers say, but too much of it can skew expectations and ultimately sabotage a match. People tend to read too much into emails and other online conversations, which increases the potential for misunderstandings and disappointment, they point out.