The extinction of languages

Sally Thomason posts at Language Log about the death of an obscure language.

I just heard on NPR that Marie Smith Jones, the last speaker of the indigenous Alaskan language Eyak, has died at 89. There's an AP article about her here: she was the last full-blooded Eyak; none of her numerous children learned Eyak because, as one of her daughters put it, they "grew up at a time when it was considered wrong to speak anything but English." Michael Krauss, a professor emeritus at the University of Alaska Fairbanks and the world's most prominent expert on Native Alaskan languages, worked some years ago with her and two of her relatives to compile a dictionary and grammar of her language, as well as a collection of Eyak stories. But for the past fifteen years, the AP quotes Krauss as saying, Jones was "the last of her kind...With her death, the Eyak language becomes extinct."

Is the dying out of a language automatically a bad thing, especially if only one or two people actually speak the tongue? What made Eyak so special that its loss should be mourned?

I'm not trying to be an English language snob here (though I'm fully aware that I may come across that way), but I truly am intrigued by the notion that a language's preciousness could be measured by the declining number of people who speak it natively. The fewer people, the more precious the language, apparently. But that can't be all of it. If that were so, then any number of extinct languages could be hailed and mourned.

The reason for the regretful tone of Thomason's post must be that Eyak was supplanted by English, in which case I see no real reason for mourning the loss outside of the tired denouncements of colonialism. This comes from a man of Irish descent. I know not a word of the Irish language, yet I do not feel any particular personal loss for not knowing the tongue, and I doubt I would be very sad if Irish actually disappeared from the Earth. I am fluent in English, which is actually my native tongue, and I have studied the language extenstively and have a healthy respect for its complexities. And this is the language of the people who historically oppressed my people. Is this a particular bias? Does anyone think I'm wrong because I like English and I don't hold affinities for little-known languages?