The diversity of anxiety disorders are the most prevalent of the DSM-IV-classified psychiatric conditions as a group (estimated lifetime prevalence of 24.9% according to an early nineties survey). As a widely under-diagnosed and under-evaluated condition, most of its economic impact on health care systems comes with the associated physical symptoms rather than with the (generally inadequate) treatment itself.
As a media subject, anxiety disorders doesn't have neither the "flavour" of bipolar's elated euphoric mania (which apparently generates a huge number of stupid young people who "secretly" self-diagnosed themselves wanting to live an Andy Behrman story), nor the excrutiating pain of clinical, neurologic-based deep major depression. There's somewhat of a jest in media descriptions of people who can't do a number of minor daily tasks such as drive a car or leave the house, and also a general sense that that's a quite manageable condition easily solvable with few sessions of cognitive-behavioral and exposure therapies. Nevertheless, some patients remain refractory even to various combinations and doses of pharmacologic drugs. A common problem in patients with "treatment-resistant" anxiety is the use of inadequate doses and treatment duration with specific medications. SSRIs (Selective Serotonin Reuptake Inhibitors) and other drugs claim to work by correcting chemical imbalances, but without accurate tools to measure neurotransmitter levels it's difficult to know if one's correctly targeting a defficient neurotransmitter, reaching a desirable level, or even introducing a new chemical imbalance and abnormal brain states - resulting, e.g., in persistent sexual dysfunction. Hence, diagnosis may need to be periodically reconsidered, and comorbid diagnoses carefully accessed.
Meanwhile, there's a small series of known or promising powerfull therapeutic alternatives (i.e. non-pharmacological) that it's not first-, second-, or even third-line treatment options at this point - e.g. vagal nerve (electrical) stimulation. Think of all the suffering and impaired functioning of a (traditional) treatment-resistant patient with, e.g., 20 years of illness, 18 different combinations of medications with all sorts of mainly unpredictable side-effect and interactions profiles. I.e., 20 years during which the patient was busy running away from the pain - a life organized around the not so simple task of not feeling pain. A patient who eventually will consider suicide as a serious (self-)"treatment" option, because of all the treatment-resistant doctors.