Sure, Google are huge in the field of search engines and may have limited growth potential here. And sure, both global and local marketing may be diminishing. But still there are enormous possibilities for Google. If we view the marketplace for ads as a whole, Google are still very small and they offer something unique.
In the fields where I have my websites and those other fields where I make many searches, I still see very few adwords, but the number is growing almost day by day.
From my logfiles I might make a long list of search terms that are certainly not among the most searched but still have unused possibilities in them. I do not doubt that others eventually will see these possibilities too, put bids on some of these words and have clicks.
And I do not doubt that there are hundreds of Danish words (and thousands of words in other languages) with unused potentials that are larger than the ones that I know best.
Just think of all those small and not quite so small Scandinavian companies that would like to have a share of the market in the other Scandinavian countries. They may find it more relevant to buy adwords than to optimise pages in other languages than their own.
And just think of all those commercial websites that may be created in languages that still have a rather small presence on the web.
I can hardly imagine that I will ever bid on adwords myself, but I easily understand why others do. That market has only just begun.