Version 2.0
Version 1.0 added configurability to this extension, allowing users to choose which sites the extension was active and inactive. That change meant that a new version of the extension did not need to be released each time a new site needed to be added to the "whitelist" (sites where the extension was inactive), but it did mean that users were responsible for configuring the extension to meet their needs. Additionally, for backwards compatibility with older versions of this extension, the default configuration was to blacklist all sites and whitelist a few, but I believe the opposite is a better solution: whitelist all sites and blacklist only the troublesome ones.
With the release of version 2.0, all sites are now whitelisted -- meaning this extension does nothing by default -- and users need to add to the blacklist any troublesome sites that they visit. Adding to the blacklist can be very quickly accomplished by using the "Browser Action" button.
The easiest way to add a site to the blacklist is to click on the extension icon 
, then optionally edit the auto-generated pattern, lastly click "Save":
After that, the extension icon should now be blue, meaning the extension is active for your current tab: 