I am addicted to Traveller as well, as is a good portion of my family. Having never tried Black Tar Heroin, but having experience in seeing the effects, I'll take gaming as a vice, if it can be called that.
For me I got hooked on the metal engagement of the activity, along with the incredibly strong bonds that gaming made between me and my freinds growing up playing. I also went to a pretty clicky high school, and I can say with all certainty that I would have much rather been rolling the isocohedron with my freinds than I would watching someone else barf at a keg party.
The computer stuff is a pickle for sure. Neurological studies are showing that limited mobility patients playing mmporgs have the atrophied parts of the brain reserved for muscle control stimulated when playing. That is some strong stuff to mess with. I also had to have a talk with a co-worker, because he was banging out of work to play Call of Duty 4 for days at a time. Computer gaming has definitely changed our culture. Even Atari did.
I've only known one guy that went nuts, and it was pretty tragic. He went from affirmed master DM to roadside tent evangelist to inpatient. A very disturbing episode.