You sneak around corners in forums, read blogs in shadows, and don't leave one scrap of evidence you were there. You, my stealthy friend, are lurking.
Think nothing harmful comes of it? Well, you're right but nothing exceptional does, either.
When you lurk:
1. You don't get the mutual benefits of networking.
2. You shut yourself off from more social activity.
3. The opportunity to ask questions is gone.
4. The chance to share knowledge you possess is wasted.
5. You could even miss out on new friends.
If you do read without commenting somewhere, make sure it isn't a full-time arrangement. There is much here if you just try.