The OP's point about a 20's dom with 7 years experience does raise a great point, one that really brings up the whole idea of being skeptical and investigating before jumping in.
Not only would verifying a dom be a lot of hassle it would effectively be impossible, how would we assess experience?
I guess my point here is there is no substitute for personal responsibility. Do your research, do not take one ad at face value, ask questions, ask others questions, ask for references if needs be. There is a pervasive misconception that asking a dom questions is a no no, that's just rubbish. Anyone can type whatever they please, "I have 100 years experience as a Dom and have trained over 200 subs, bow down and worship me!"
Yes it's hard to find a good dom but why does the responsibility for that come down to anyone else but you? You know what you want, you know what you like but just because someone says things that sound great doesn't mean you throw out all caution and submit to them without question.
So what do you do?
If you see an ad that sounds interesting click on the member and look at their other posts, read their profile, does it add up? Does this person seem consistent, do their posts follow a similar theme, do they seem real or too good to be true? If you find only a string of the same posts, or no other posts its time to hold the phone, regardless of how perfect this dom seems work a bit, spend some time and curb that enthusiasm.