Note: this trick doesn't work in Firefox now that Google defaults to https. Firefox won't send a Referer header when you're going from an https page to an http page, so wsj.com doesn't know you're coming from Google. (I don't know whether it sends one for https-to-https cross-domain links.)
Ninja edit: that is, this is how my Firefox behaves. Not sure if it's caused by an add-on like HTTP Everywhere or something like that. But it seems like I read something from the DuckDuckGo blog describing this behavior.
Chrome sends a Referer of "https://www.google.com" (i.e. just the domain), so wsj.com lets you past the paywall.