Item 2) Professional reviewers have purchased multiple products above certain threshold.
Easier way to stop this is to prevent reviews from people who used a coupon to buy something and the price is above some threshold (i.e. seller doesn't knock to $5 between 10PM and midnight for their reviewers to buy it).
If I can think of this solution - why can't Amazon? Simple answer is they know of this behavior and encourage it.
I have shifted my purchasing behavior to buy from Walmart, Target, Ebay when at all possible. I know Walmart isn't exactly an angel - but I'd rather have 2 devils in the marketplace than 1. I even try to buy books from Barnes And Noble...but unfortunately the fulfillment time + price is hard to beat w/ Amazon. I rarely have books above the B&N threshold for free shipping.