Absolutely. And note that in other areas (such as payment fraud) they put in a lot more legwork because the consequences actually hit them directly instead of just their customers.

It's either that, or they are failing really miserably at controlling the flood of bogus/fraudulent review.

I find the latter hard to believe. We're not talking about a mom-and-pop shop here. This is Amazon, they employ many thousands of very smart people that could no doubt build solutions that are better than the status quo.