This extension circumvents certain techniques used by Google and Facebook to track link clicks.
When you click a link in Google search results, Google uses JavaScript to replace the actual link with an indirect one, which they use for click tracking. Google then redirects the browser to the actual destination after logging the click. DirectLinks disables the JavaScript that replaces real links with indirect ones, so that when you click a search result link, Safari goes straight to the destination.
I’m in because that pisses me off.