Considering that whenever I google a programming question, the most useful answer is generally on StackOverflow and at the top of the search results, I have a hard time considering it harmful in any way. It might not be perfect, but I don't know anything better.
Considering that whenever I Google a programming question, the most relevant question has been moderated into oblivion and so I have to seek my answer elsewhere.
Above is a bit toungue-in-cheek, but it is true in many cases. I don't find SO as the definitive answer site for that reason, but there is a lot of good information there.
The author of the article isn't saying it's harmful for people searching for questions that already have good answers.
He's saying that people who contribute heavily to the site with answers, knowledge and moderation are probably better off spending that time doing something more productive.
And with the gamification system keeping them at it, it harms them when they could be doing something more productive than chasing Internet points.
Probably. And I probably should have done something more productive than building up 25K reddit points, but I don't blame reddit for that. If I'd spent the time on stackoverflow instead, it might have been more helpful to people.
How's it different from mailing lists? IMO after a certain stage the gamification aspect goes away (for high rep users) - that's not the reason they contribute.