Totally depends on the article and expected audience. For me, Twitter is for articles that are startup/tech related. I work hard to maintain my public persona on Twitter and really filter what gets posted there. I syndicate everything from Twitter to Facebook. Facebook is for funny stuff my mom will like. Email is for specific clusters of folks that will find the article relevant, though I usually end up sending articles to the same 2-3 groups of people. My blog is a special case. I only post stories there that I think reflect my personality and deep interests.
Also, after an experiment that automatically posted my Google Reader starred items to GroupMe via http://ifttt.com (awesome service), I've decided that SMS is the wrong way to share articles.
I find myself emailing news stories to the same email group over and over, but unable to find a history of what we talked about.