Daniel Amen is a snake oil salesman/quack, "the most popular psychiatrist in America", a brain disorder "specialist", and a bestselling self-help author guru. He co-authored a diet/"Biblical lifestyle" book with Rick Warren, Mark Hyman and Mehmet Oz.
Amen is the founder of Amen's Clinics, a group that has commercialized the use of a now outdated type of brain imaging technology, SPECT (single photon emission computed tomography). While it makes for interesting experiments about large groups, it has not been shown to be an accurate and reliable diagnostic tool for individuals, meaning the couple of thousands of dollars each of his ignorant patients have spent was wasted on a tool that is by definition not justifiably useful for what his groups have been selling it for. Using such an expensive diagnostic tool for even simple problems violates the standard of care of medical professionals to follow the most appropriate diagnostic process for each patient.
Most attempts at diagnosing a single average person based off scans of neuroanatomy are destined to be little more than a guess, either inaccurate, coincidental, or just vaguely familiar as a result of the Forer Effect. Much like the newer, more fashionable PET brain scan pseudo-scientists, he looks at a brain scan, thinks about how "______ disorder is correlated with low levels of brain activity in a certain part of neuroanatomy", and rattles off a few vague predictions that could fit almost any kind of person ("You are happier when you are busy"). 
The ethics of neurodiagnosis
Functional brain scans are simply not the correct tool to give an individual an accurate and reliable diagnosis, so the entire concept of Amen Clinics does not help average people so much as make money off their ignorance; they are not better equipped to help individuals than any other kind of "mental health specialists". Brain scans are only useful as a means to collect wide swaths of exploratory data which is later statistically correlated into the "high/low levels of activity" you always read about on the news.
Amen Clinics has scanned 50,000 people at an estimated cost of $170 million, which would be $3,400 per person ("10 percent discount if you bring along a member of your family"). Most insurance companies won't reimburse any of that, too bad such a potentially useful tool hasn't been shown to be effective under peer review! Most of his patients have been found to be unaware that SPECT scans are not founded on solid evidence, or that a regular psychological specialist could help diagnose them just as well as a functional neuroimaging test.
Dr. Amen expressed the belief that presidential candidates should be brain scanned to see if they would be dysfunctional leaders or not,  which might be a feasible idea if technology improves past this new frontier of silly and egregious neuromarketing.
Apparently a single of these seemingly pointless scans gives a similar amount of radiation as standing on the Chernobyl grounds in 2010, for half an hour.
Not only are the tools his clinics use ineffective for what they use them for, but the treatments suggested are often pseudoscientific as well, ranging from mainstream therapy and psychiatric medications to hypnosis, prayer, meditation, biofeedback, dietary supplements, hyperbaric oxygen treatment, transcranial magnetic stimulation, and eye-movement desensitization. Dr. Amen sells a variety of branded 'natural' vitamins and dietary supplements, including one that is labeled as "preventing or stopping" Alzheimer's. He somehow managed to get PBS to air his self-produced infomercial on "the prevention of Alzheimer's disease", to the complaints of many people.