I wouldn’t call it hacking Google, but they’ve tricked it.
Google’s algorithms partly use link text to determine a site’s ranking. So, if a lot of sites link to http://boards.straightdope.com/sdmb with the text “The Straight Dope”, it increases the ranking of that page in searches for that text. The degree of affect a link has on rankings is related to the popularity of the site it’s on, so a link from CNN.com would have a more significant effect on the linked page’s ranking than one from Joe’s Discount Floor Tile Superstore.
So, what’s happened here is that a lot of jokesters with popular sites (usually blogs) decided to link to Bush’s biography on whitehouse.gov with the text “miserable failure” (apparently this has gained enough momentum for “failure” alone to work as well). And thus…
Some people call this a failure of Google, but I disagree. Their engine is accurately reflecting the content of the web.
This is known as a Google bomb, where users manipulate the Google search rankings by linking to a site using certain anchor text. In W’s case, his official White House bio was linked to via the words miserable failure.
Since this one is answered, I’m closing it. If anyone wants to continue a discussion, perhaps MPSIMS, IMHO, GD, depending on what you’re trying to say.