It's possible to get addicted to anything in life, anything. Drugs, hobbies, dreaming, food. Psychologically, of course. Only certain drugs cause physical addiction.
If something is psychologically pleasing, it has the potential to become addictive. Has anyone become addicted to LDing? Not that I've heard. I doubt anyone has. I highly doubt anyone will.
It differs from addictive hobbies like video games in that you can enjoy lucid dreaming while you sleep and enjoy real world hobbies while you're awake - things like WoW take up all of your real world time. If anything, lucid dreaming has improved the waking lives of many people, rather than taken over their waking life.

Yes, you can feel pain. The brain can't distinguish a dream from reality very well (especially a non-lucid). I've been injured in both non-lucid and lucid dreams, the pain will sometimes linger even after I've woken up. It's nothing to worry about, though. It's typically very dull pain.