We basically tried the equivalent of this (placing relatively free fonts unknown on most platforms first) which Kaldari talked about previously. Ultimately that kind of declaration is useless for the vast majority of users and we got very specific negative feedback about it on the Talk page. These fonts are ignored by most systems when placed first or when placed later in the stack. Systems match the first font they recognize, so using something they don't recognize or putting it later is a largely just feel-good measure.

The whole Arimo/Arial conundrum is largely a matter of the fact that Windows users simply do not have a Helvetica-like font available on most versions which is better than Arial, warts and all. Again, the best solution is to deliver a webfont, which most people with good design sense are doing these days, and we can't yet. 

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