Beware of any "celebrity rabbi".
A rabbi (and lehavdil, a priest or other religious leader) is supposed to be a selfless, humble person by nature. Any so called "rabbi" who seeks fame and popularity is in and of itself in direct contrast to the very nature of what a rabbi is supposed to be. This is the ULTIMATE red flag.
Yona Metzger, Shmueli Boteach... the list goes on.