This excellent article delves deeper than just the 1% of people who contribute active content, the 9% who contribute and 90% who supposedly just "lurk" to point out that an MIT student says that:
"Upon further research I found, in an MIT study, a defense of lurking that was better than anything I could make up. The study found that active lurkers in an online community might constitute closer to 40 percent to 50 percent of members and, while these people might not contribute directly to the online forum, they contribute by taking some of the ideas from the specific community and sharing them in the world at large. I propose we call these people "worker bees" instead of lurkers, as they take the pollen from one online community and spread it to others. (I think "worker bee" sounds much better than "lurking" also, but I don't think I want to go too much further with a pollination analogy.)"
I think that worker bees is a good analogy - they take content out to the world. I hesitate to disparate 90% of those on networks because their sharing cannot be measured! They are valuable too!