Playing with more AdSense

I am trying to find a golden median between the amount of clicks on Internet Polyglot pages and people getting ticked off by too much advertisement.

As an experiment I put a small ad bar inside the lesson list, a bigger horizontal bar on the lesson detail page between "Back to lesson list" button and "Play lesson" links. Also I put a huge rectangle ad on the "Dictinary" articles. Let's see what's happens next. As the main goal of the site is to provide a quality free service to language learners, placing the ads should not compromise this idea and make browsing of the site unpleasant.

The main motto of Internet Polyglot: make site useful so that people return to it!