Why do I need keyword based filtering for AdSense

Imagine a website about the Half-Life 2 game. It's in Czech, while AdSense for Czech content is available for about two months, therefore there are not many advertisements leading to not to high bids.

As a Half-Life 2 website it's full of articles containing words like "Valve" (meaning that software publishing company), Source (3D game engine) or Steam (software for game distribution). And of course lots of Czech texts.

Now, when AdSense servers try to match the appropriate adverts for my web, they most probably choose the one with for the word with higher bid. So mostly adverts for Steam sterilizers, water controls or in the best case software development. And of course in English. I can't speak for all of the visitors but I'm sure most of them aren't interested in those topics and when the click on them, they do by accident. So it's a lose-lose-lose situation for me (less income), Google (the same) and the advertisers (worse conversion).

Yes, there is a possibility to filter inappropriate ads by their URL, but first it doesn't work well (too many times I see an add blocked many days ago) and there's too many unwanted ads that I'm unable to filter them all out.

There would be few ways how to get rid of them:

1. Google fixes it's algorithms so they take into account not only the words but also their context (most difficult and improbable)
2. Google fixes it's algorithm so the ads in different language have lower priority (but maybe they use it already but the priority for Czech ads is still too low)
3. Google let me choose what words aren't relevant to content on my site

I hope it's obvious the latter is the best. It can't be misused to get irrelevant but high-priced ads and it would enable me to tell the algorithm, which doesn't truly understand human language, what are the irregularities in my texts. Fortunately people in Google are preparing this function and it's even said it's in beta testing. So I hope it will be publicly available soon (or that I will be invited to beta testing - do you hear me, someone from Google? ;))