The domain and nickname freeloader service monitors and reserves both domain names and usernames on a variety of social media for a very low monthly fee (for monitoring) and success fees (when the service indeed secured a domain or nickname for you).
You can also sign in to a higher monthly fee. In return, you get advise on what social media are growing fast and where you are not yet present, you get secured your preferred username (+success fee?) so no-one else gets the change to run off with yours.
The freeloader service also sell domain names and offers bartering services for both domain names and usernames. Obviously.