If you think about it, the numbers aren't surprising in the lightest - Lnux users aren't using a Microsoft-based a search engine. It is interesting to see that Mac users are following the same trends, however - also snubbing Bing overwhelmingly in favor of Google, and in a small way Yahoo. With both Linux and Mac markets growing - Macs moreso - getting viewership from both camps will be more important to Microsoft. Bing, however, is just not having an impact on them.
Not that Bing needs a Linux user audience to be successful. As an unfortunate minority, Linux users (which includes myself) are simply too few and far between to influence these surveys and concern Microsoft - who has enjoyed relative success with their new search engine.
If Redmond is to gain Linux viewership down the road, it will probably be through functional (and free) APIs. Google has a plethora of functionality already available, such as the implement ion of AJAX Search API - which is probably a lot more useful to a developer than anything else.