I have actually done some reading on this. And this is covered in depth on one of the seasons of Dr Drew. They bring in sex addicts and you learn quite a bit about it. In the case of the 8 or 10 participants this is a little summary
Some are addicted to the physical chemical reaction, like any other drug
Some are addicted to the romantic side of having sex with someone new
Some are addicted to fresh love
All people required this to be NEW. Old partners etc, could not fulfill this need. So increasing the number of times you have sex with your wife would not make it better.
All three groups demonstrate these addictions by having sex with anyone they can. In the midst of what is pretty crappy television there is some good information released.
Obviously the show was a small segment and involved "stars" who were addicted. So it is a small subsection of narcissistic people. But it was interesting to watch how the addiction is more akin to chemical addiction than simply masturbating all the time. They really were craving that chemical release. One of the stars was a drummer from many rock bands. Had never touched drugs, didn'tlike to drink, but had had sex with 1000's of women. He had made the connection that his addiction was no better/worse than the guy addicted to heroin.
I think non-monogamy does attract sex addicts (hell how can't it, its pretty much an open door). We see serial monogamists become serial polyamorists. We see people jumping from person to person trying to get a fix, before NRE is even complete. Unfortunately that will be the connection made to non-monogamy, its bound to happen and you can't fault the general public for this connection as sex addiction becomes more prominent.