Firefox will reportedly drop Google search as the default search engine in favor of Russian-based Yandex in official Russian builds of version 3.1. According to Mozilla General Counsel Harvey Anderson, the reason behind the change was a study of Russian user behavior conducted by Mozilla that concluded that Russian users wanted direct access to Yandex more than they did Google.

That’s not overly surprising, since in Russia Yandex controls the search market at about 43-45% of all searches. As we reported in September, there are just five countries globally that Google doesn’t currently dominate — Russia being one of them. Interestingly, though, among those five countries, Google is actually competing at the highest level in Russia, where they have about 35% of all searches and have actually grown their share of the market by about 6 points over the past year.

Losing default status on Firefox will be a pretty serious blow to Google in terms of competing in Russia. Just over 21% of Russian Internet users browse the web using Firefox, and about 17% using Firefox 3 — which means Firefox 3 has upped general Firefox usage in the country by about 5-6% since being introduced, according to LiveInternet.ru statistics. Last April, just about 15% of the population used Firefox.

We wrote last month that Mozilla’s relationship with Google has become increasingly complicated since Google released their Chrome web browser. It’s not clear what, if any, cash has changed hands by switching to Yandex as a default search engine, but because Google accounts for about 88% of Mozilla’s revenue (via a search advertising deal), it would make sense for Mozilla to start seeking alternative sources of revenue.

We’ve predicted that Firefox might suffer once Chrome matures, so seeking new revenue streams is a good idea for Mozilla. If Google can’t be relied upon as much for support, Mozilla will need to start forging partnerships elsewhere.

Though Anderson said the reason for the change was a user study, we suspect that at least part of the motivation for the switch to Yandex was a tit-for-tat reaction from Mozilla to Chrome. There is no real indication of that, however, so it’s a hunch on our part. Russia is a good place for Mozilla to start seeking alternative revenue partners given that Firefox both is popular and Google is not the dominant search engine — that’s not a common dual occurrence.