Today, Opera announced they bought AdMarvel for at least 8M$
After Google with AdMob and Apple with Quattro Pro, it's the 3rd 'browser maker' which acquire a mobile ads network.
Now, think a little :
you BUY an Android's phone, an IPhone or any other phones (which support Opera) to see ads and so they earn money...
or, if you prefer, they SELL their products to EARN revenue from their ads...
you pay to help them earn more and more...funny now ?
It's like if Ford was selling a car which needs a special gazoline...made by Ford