Unhealthy habits are unhealthy. Playing games consequently for long amounts of time is bad for us, both physically and mentally. This isn't something we can deny just because a bunch of overly excited censorship advocates are out there screaming "GAMES MAKE YOU CRAZY".
Can deny it's a necessary consequence of such practices, though.* Least I would, having been there, done that (more than once in the case of the two-days-straight and several dozen times in the case of playing through the night), and experienced no hallucinations (of the nature described, anyway**). So it's not so much "unhealthy habits are unhealthy" as "certain portions of the population have particular reactions to specific habits", evidentially unhealthy or not (since there were apparently those that experienced the phenomena with considerably less contributing factors than overnight or 48 hour gaming binges).
I do have to say, though, I'd love to see the study expanded if similar ones haven't already been done. Seems obvious to me you should see similar reactions from reading, watching TV, and music (the catchy tune phenomena is an obvious parallel) at the very least -- I'd guess other stuff as well, such as writing, working, and so on. Anything a person might do for an extended period.
E2: What would be really interesting would be if they could get the same study groups (along with other, different, ones of course) in on said other experiments, to see if it's medium specific or influenced, or not.
*E: Which I don't remember the article stating, but your wording suggests it a bit, so making the statement above to kinda' preemptively nip the concept in the bud.
**Visual snow yadda yadda 24/7 visual hallucinations etc.