There are, in fact, two separate pro-ana "movements" - both of which function mostly via the Internet. One movement (let's call it M1) attempts to glamourize and glorify a horrifying disease (this would be the group that gets the most publicity); the other (M2) acts as a support for those who suffer from Anorexia Nervosa but are not yet "ready" to recover.
If a person does not want to recover, no force on Earth can make him/her. Even if he/she is hospitalised and forced to gain weight, all he/she is going to do as soon as he/she is released is start over, anyway.
M1 websites/communities encourage disordered eating and reinforce unrealistic ideals of physical perfection, offering dangerous tips on how to lose weight faster. These are the groups that promote Anorexia as a "lifestyle choice".
The goal of M2 websites/communities is to support and protect genuine sufferers, while also pursuading those seeking to develop an eating disorder to find safer ways to lose weight or simply to learn to love themselves as they are. These sites/groups often show examples of "bad tips" (eg. using a Lifesavers mint tied to a piece of dental floss to self-induce vomiting, which is incredibly dangerous) and usually list ways to actually minimize the damage caused by long-term disordered eating and binge/purge behaviour (eg. swilling/gargling bi-carb in water after purging to neutralize acid in the mouth, taking multivitamin and mineral suppliments, etc.). M2 sites/groups discourage laxative, diuretic and diet pill abuse, often giving graphic warnings of the long-term effects of these, while M1 sites/groups often encourage such dangerous habits.
In short, some pro-ana sites/communities are having a positive effect on the growing epidemic of eating disorders, keeping many chronic sufferers from committing suicide or succumbing to complications of their illnesses; however, many, which encourage disordered eating and behavioural patterns, are fuelling this epidemic, destroying young lives and dividing families.
PRO-ANA is NOT just ONE movement.
ACTUAL M1 pro-ana welcome message: "The Goddess Ana offers us perfection and asks only for our complete devotion and dedication in return. Serve her and she will grant you thinness."
ACTUAL M2 pro-ana welcome message: "Anorexia Nervosa is a deadly disease. Once you have it - assuming you don't die a long, painful death from malnutrition - you will never, ever be truly well again. You will spend the rest of your life feeling empty, lost, alone and inadequate. If you have come here looking to "get" anorexia, I recommend you do your research on what that actually means before you make up your mind. There is nothing beautiful or glamourous about Anorexia Nervosa."