I don't think Runescape prevents drugs, alchohol, etc. They can both be done. And whether this is healthy or not can be argued, it depends on your definition of healthy. I mean, the common perception of all computer games are that they are bad, and people over 13 shouldn't be playing them. But that's just an image, people who think that never experience it. I don't think my runescape "addiction" is healthy, or directly preventing me from bad influences, but I don't think it's an unhealthy addiction either.