A lot of decisions, regarding how scammy or legit a service is, are based on intuition. I'm in a position that allows me to interact with the teams running the services we list for days, often weeks, before they're listed. I tend to also ask them what region they're from. That's usually enough information to develop a gut feeling about people.
I could probably compose a list of red flags and green flags, but I'm a little concerned someone might try to game it.
I was most interested in this. The reason is that most exchangers (especially new ones) make a significant announcement when they are listed on a monitoring service, in some way they raise their trust score by using the rating of a monitoring service.
I'm not against new services, I'm just interested in the verification procedure that aggregators do before listing them.