http://www.robotstxt.org/ I imagine if you have a user-agent: * and disallow: ALL that it would affect earnings.
The only real thing to be concerned about is to make sure it validates and that you don't exclude legit crawlers...Google's webmaster tools will help you with the former.
I could not understand. Take massmirror as an example. Look at their robots.txt They block all robots but then they got authority in google. So, meaning even if I block robots, I can still be indexed normally by google? No penalty will be given right?
What specifically in robots.txt would affect your earnings (I mean, other than what I said about having it disallowing robots, including the adsense crawler which may actually be a different beast)