Cheating and having affairs has been going on long before there were computers, social networks, or texting via cell phones.
When affairs begin in the work place no one says the divorce was caused because a person had a job.
Affairs/cheating like everything else evolves with the times.
The cause of the divorce is not the technology/tool used.
People appear to want to blame tool for existing.
Awhile back I wrote a hub on this subject called,
The only thing technology has done is make it "easier" for those (who want to cheat) to be able to cruise the web at home/work looking for love/lust as oppose to having leave the house.
They don't have to make excuses to go out to nightclubs or bars.
However when you get right down to it (the person) makes the choice to use his/her computer anyway they see fit.
"A fork can be used to eat a salad or to eat a large hunk of double fudge chocolate cake!"
Cheating is a choice.