It's not just the number of reviews that can reveal a shill, it's also the marketing-like language employed. Not a few reviews are worded like the below. No real reviewer would write like this.

"I enjoyed the crisp, 150-thread count, imported Scandanavian comforter. The tasteful rosewood desk and the authentic Herman Miller chair complemented the well-stocked, conveniently located mini-bar."

Oh, puh-leeze!