They recently compiled a list of the top 250 reviewers. The bottom two folks on the list had 25 reviews listed.
I'm also a reviewer (for The Oregonian), but Publishers Marketplace only lists 24 reviews for me. I've actually done more - just had one published a week ago, in fact - but I guess some haven't made it on line, and thus not into the database. I would love to be in the top 250, for no reason except that it sounds cool. With about 50 reviews, you could get into the top 100.
My proudest moment as a reviewer lead to my name being in the New York Times Sunday Book Review. An ad quoted my review of Evensong by Kent Haruf, using my words, "Spare, delicate and beautiful." And unlike most ads quoting reviewers, it used our names.
Occasionally I will look inside paperbacks to see if they used my review in the front material. It runs about 50-50. Maybe The Oregonian isn't big enough. Maybe it's like the South Dakota News & Express or something...