Do Google adsense have an obligation of reporting your income to respective income tax authorities ? I believe in USA, yes. But other countries, no. Am I wrong ?
You're supposed to report it yourself. It's not like it would go unnoticed if you started making a lot seeing as you have to put the money in the bank.
As an adsense publisher, you are responsible to report your own taxes. The correct tax form associated with being an individual adsense publisher is a 1099 (the form for being self-employed). You may report your earnings if you make under $600 through Google Adsense. But you are not actually required by the federal government to report your earnings in the U.S. unless you make over $600 during the tax year.