Here is the list for the Boston area. These are contractors, painters, so called licensed electricians, apprentices, moonlighters, one guy for $20/hr, septic tank inspector, handyman, ripoff artists and other undercutters.
Some list under multiple names with the same email and phone numbers.
In MA if you advertise, you must include your license number. Your license must have your business name on it.
Most of these people don't even give their names.
Some say licensed and insured. Can't verify any licenses without the numbers.
Some of these are for same guys (multiple ads). I can only assume they are getting some work from these ads. I would say out of this - partial - list, there are only about 8 ppl....so far.