When I was searching for domain names, I thought "hey, what if someone collects these names I'm searching and purchases them hoping to have me buy it from them?"

Well, apparently this is a real thing. People search for available names on certain sites, and some collect their search queries and claim the name so the seeker has to buy it from them. Other legitimate sites do not do this.

How do we know which sites are legit and which are not? Register.com seems to be the #1 choice. Is this site trustworthy?