I fly frequently as well. In many small airports, they try to push ALL people through the rape-scanners. The same policy is in effect at major airports depending on the terminal.
I also have dark skin.
Ever gone 7 flights in a row and get "randomly selected" for further screening? Ever had your genitals grabbed by a TSA agent? 4 times during one screening?
Ever been kicked out of an airport for refusing to be scanned? Had your flight cancelled by the police? Been surrounded by police and TSA for refusing a scan?
I have. Believe me, it's not fun.
Dosimeters are not that expensive, and they would go a long way towards making people feel more comfortable, but regardless of cancer risk or radiation risk, the TSA creates a violation of personal privacy, security, and comfort. They do so without providing even a fraction of a security improvement. I would even go so far as to say that security is worse with TSA in place.