The divorce rate has been rising for decades, way before the internet was common. The internet might increase or normalize marginalized groups who usually have a social stigma - but divorce isn't in that category. Divorce has been common for a few decades now, the internet really shouldn't effect it in any way. In fact, in 2005, divorce rates were the lowest they've been since 1970. And divorce is in a downward trend overall. Maybe because couples experiencing trouble can access information on marital counseling and get answers from couples going through similar situations - thanks to the internet.

If you're asking if the internet leads to greater infidelity, tough question. Interestingly enough, the internet - with its anonymity and feelings of control for the user - is allowing researchers to study things like this and get more honest answers. Due to people trusting that their responses will remain anonymous they are more likely to tell the truth, so the data doesn't always line up when compared to non-computerized studies.

Contrary to popular belief that the elderly come from a different time and take marriage more seriously, research shows huge increases in infidelity in people over 60. There's been some increase in the infidelity of women, but the reasons for this (and if it's even an accurate statement) are unclear. There is more talk about people meeting online, or having virtual relationships, but this could easily be just because the internet is becoming increasingly popular and common. Its entirely possible that the internet is facilitating adulterous relationships, but that the people being unfaithful would have been unfaithful anyway. In other words, the internet is just another medium for communication, we can't really blame our problems on it.

.... Also, what craigslist are you on? No married for married section in Chicago. There's m4m, meaning man seeking man.... that comment was just confusing to me.

Sources: http://www.divorcemag.com/statistics/statsUS.shtml
http://www.bsos.umd.edu/socy/vanneman/socy441/trends/divorce.html
http://www.nytimes.com/2008/10/28/health/28well.html
http://www.divorcerate.org/

McKenna, K.Y.A. and J.A. Bargh. "Plan 9 from Cyberspace: The Implications of the Internet for Personality and Social Psychology." Personality and Social Psychology Review 4.1 (2000): 57-75.

McKenna, K. & et. al.. "Relationship formation on the internet: what's the big attraction?." Journal of Social Issues 58.1 (2002): 9-23.