Amazon's Perplexing List of Top-Rated DVDs

My mind was a little blown by Amazon's list of top-rated DVDs.

#1 doesn't surprise me. "Food Production Systems for a Backyard or Small Farm" sounds like exactly the sort of thing 224 people would go absolutely apeshit crazy for. Fair enough! But #2 and #3 are two not particularly popular, not particularly well-reviewed TV shows: "GCB: The Complete First Season" and "Person of Interest: Season One". Why them??

From my experience running Chowhound, I'd be inclined to suspect ballot box stuffing, but that can't account for the complete lack of negative votes (of GCB's 553 reviews, only a minuscule 7 are not five-star).

Next is Mean Girls, rated five-star by over 96% of 4800 reviewers. The movie was popular ($130M gross), but not Star Wars popular ($775M gross). And it was reasonably good (83% rating on Rotten Tomatoes), but it ain't Citizen Kane good.

So what's the underlying dynamic? I'm guessing a complex set of factors. All are clearly/narrowly targeted enough that they wouldn't likely be bought by people who weren't previously bought-in to "that type of thing". They're niche, but not so niche as to turn off niche haters. And all are a notch or two below massive popularity, making it less likely that purely random customers would wander into purchasing and dilute the unanimity.

Also, while none of these are great works, they're all smoothly competent and have no gaping flaws or potentially annoying or abrasive elements. Contrast with Napoleon Dynamite, which also has clear/narrow appeal, moderate popularity, niche crossover appeal, and whose 1289 ratings are dominated by 626 five-stars, but which also draws 299 one-star ratings...surely in reaction to the love him/hate him protagonist.

Can anyone think of other factors in play?