[__--__]

There very well may be a limit to the propensity of the brain toward addiction, unless we delve into deep sci-fi territory of complete reward structure take over.

What makes you think that doesn't happen? We know the brain is plastic. More frequently used neural pathways get reinforced, unused ones get destroyed. After a long period of addiction, the brain is physically altered to require that addiction. The presence of the addiction becomes the new baseline for feeling "normal." There's a limit to this for physical addictions, because there's a point where the heroin will kill you. Psychological addictions don't have that restriction.

[olefoo]

Psychological addictions can be just as deadly as physiological ones. Death from overwork[1], death from playing video games[2], death from avoidable STD's all of these could be classed as deaths resulting from psychological addictions.

1. http://en.wikipedia.org/wiki/Kar%C5%8Dshi 2. http://www.ranker.com/list/8-people-who-died-playing-video-g...