There are people with disordered eating, and there are people with eating disorders. Eating disorders are not contagious--a person cannot simply contract one. Like all psychiatric diseases, the roots are deeply embedded in childhood and personality traits.
While I understand the concern over pro-mia/pro-ana sites, these sites are not giving people illnesses; people use these sites because they are already ill.
Perhaps one can argue that they sites are triggering and promote relapse. Well then I say to you, try going 20 minutes in this country without stumbling upon something triggering--even without using the internet. In fact, try walking a block.
On another note, I also take issue with the way in which BBC framed the article, "Pro-anorexia site clampdown urged." In fact, it took some scrolling to even see the word "bulimia."
This is only indicative of larger cultural attitudes of the diseases. Bulimia is often marginalized for a variety of reasons: 1) to the untrained eye, it can be easer to spot emaciation than pick out a purger, who is not necessarily underweight, 2) an anorectic can pack more shock value in a photo, 3) an anorectic may appear more ill by virtue of appearance, when actually bulimics are at high-risk of heart failure, among other things, 4) our culture perversely hails the control associated with anorexia, as opposed to the "excess" associated with bulimia. All of these factors contribute to the marginalization of bulimia and higher levels of difficulty in being identified as ill and in need of help.