You make good points. "Is there an objective criteria for distinguishing between good and bad obsessions?" I think that the nuance we are trying to capture is the difference between being passionate about something and being obsessed. And I think that where we can draw the line is at the psychological health of each person, although it might not be the most objective measure. Let me explain.
My wife was a national champion in college soccer. She ended up switching schools, but for the time that she was playing college soccer she got nearly full tuition. She certainly was in top physical shape. These all seem like good accomplishments, but she always tells people that she wishes she hadn't done soccer. There are small reasons like the wear and tear on her body, and her feeling that she would have more greatly enjoyed piano (which she's since taken up again).
But ultimately, the thing that she says bothered her the most was the kind of person that competitive soccer turned her into. The effect upon her personality and the way she treated other people was very negative. I won't relate the adjectives that she uses to describe herself at the time, but what's important is that the dividing line for her as to whether all her effort in soccer was worth it or not was _the kind of person it made her become_.
I'm not a psychologist so I can't really go much further with this. It probably isn't the most objective criteria, as it depends on one's value system. Certainly there are exceptions, like an alcoholic who thinks that he is really enjoying life. But if we were to talk about what seems to be more subtle obsessions, as opposed to chemical addictions, the one thing I can see that is common to both my wife and I -- her having done something that most people would have valued and I having done something that didn't result in much positive benefit -- is that neither of us liked the type of person that our activities turned us into.
What's critical is that neither of us were able to understand this until we were able to step back from our passion/obsession and look at it from the outside, as if we were a third party. We had to be able to step apart from our activity, look at ourselves dispassionately, and ask, "Is this who I want to be?"
Now, the situation you describe is a little different. To succeed as an entrepreneur requires constant education, which necessarily includes making many connections with other entrepreneurs for learning and support. Certainly someone who spends all their time consuming music might not be making the most out of their lives, but someone who spends all their time away from their family at tech conferences will also be missing out on very important things. I don't know your personal situation, but I think it does come down to your psychological well-being.
Your wealth, your social circle, even your health and your life can vanish in an instant. Whether a recession destroys your 401k, your friends leave you for other interests, you are diagnosed with a disease, or you die in an accident, there is no guarantee that any of these things will continue to persist. That's not to say that they aren't worth laboring for, but recognizing the ephemerality of these things can help give us a new perspective. What I try and ask myself is, "If I died in the next moment, would I feel that I have lived?"* That question can help me choose between another hour of Diablo 3 and spending some time with my wife, for instance. :)
Edit: For the sake of being perfectly honest, my question is a little bit different as it is based on my value system, which I'm not certain the HN community appreciates. I tried to put forth a question that most people could interpret and apply to themselves. But for me, the question is, "Do I love my God, and do I love my neighbor as Christ demonstrates His love for us, even unto death?" There are all sorts of ways -- even in soccer and video games! -- that can help me answer this question with a yes. And that's why I think the question of passion vs obsession is a difficult line to draw. To not disclose this would make me feel dishonest, but I admit that I'm reluctant to fully explain this because of the way the tech/scientist community generally feels about religion.