You could achieve the same effect with a couple of lines of CSS. As a bonus you wouldn't pop up the same alert box six times during page load for Internet Explorer users.
Not bad, but pretty buggy even in Chrome on Windows. Selecting the text sometimes doesn't de-blur it, hovering images only results in partial blur (I later realised you click to get it to work). Great idea, but definitely needs some more work before it can be considered a definitive solution for blurring out text and imagery. I forked the project and made some adjustments that were annoying me and submitted a pull request. The lack of semicolons and shorthand if statements bothered me, as did the lack of support for chainability as well. I might contribute a little more to it later on with some newer ideas and support for older browsers.
Wouldn't the spoiler still show up in Google searches? An alternative would be to obfuscate (i.e. randomly arrange the letters) the spoiler text and then make the script de-obfuscate it on-hover. Just a thought.
Less blurry is a hint? Legibility is a binary value, and beyond a certain threshold of blur, the value is false. Period. Plus, that behavior is confusing - you should have a tool tip on hover, explaining that you need to click to reveal. You should also explain any cross-browser tricks you needed to do to get it to work, otherwise people will think this is trivial and pointless.
Cool work but doesn't mix well with text selection. I'm not into js but I wonder if it would be easy to distinguish between clicking on one spot and clicking and dragging for say copy-pasting.