There's nothing wrong with single-sourcing. SecretLondon reads the Guardian, I read the Washington Times. Go ahead and quote from the Washington Post or New York Times if you want. Everybody posts info from the sources they know.
Many people think the Post and the NY Times are editorially biased, but does anyone think their *news* is untrustworthy? Okay, there was the Jason Blair thing, and the guy whose Pulitzer from 60 years ago might be revoked for whitewashing Stalin's Ukrainian genocide - but I mean aside from minor things like that, does anyone really consider them untrustworthy sources?
Same for the Washington Times: okay, their editorials and most of their columnists are conservative; but does anyone think their *news" is untrustworthy?
Uncle Ed