I'd say a study is worth it because it's part of the scientific
method/experimentation. Else it's just the so-called common sense, like the
Earth being flat and redheads being sorcerers (this one is true though).
Of course, having a source is much better (I'm guilty of that one myself on
occasions), and there is some big part of blind trust since we can't really
reproduce most studies.
Statistics, scientism, rethoric, all this makes access to the truth harder.
Yet, having studies backing statements is useful IMHO.
