OK, OK just one more go.

There is a common link between many types of addictve behaviour, (roulette, web brousing, hitchhiking, fruit machines, fishing); the random payout. Many years ago "scientists" gave a caged rodent a switch. If it learnt to press the switch, it got food delivered out of a hatch. This suited the mice well, and everyone was happy. Then they changed the rules, now only one piece of for every 3 presses. Still this was ok, it wasn't too much work and the mice felt in control of their world. But then things got strange. Now they sometimes got food after one press, sometimes after 3, sometimes after many more. Now the mice went crazy. They would stand there at their switch for hours on end, hitting it again and again. They would collect the food, but just put it to one side in a pile getting higher and higher. They lost all interest in eating because they had found a new purpose in life.