But you can only do that when you have time. I was recently investigating a product with very good reviews. They looked quite good. Then I noticed that most of them used very broken german which, when you compared them showed a pattern and looking into the users showed clearly that they were faked. But I can not trust that they are always that easy to spot, so the only possibility for me to check remains to check several low star reviews and look whether they complain about valid problems or just nonsense. The problem I see is that those fake stories are getting better and at some point will be indistiguishable from real reviews. And you will certainly not notice it when you are just quick checking several products or sellers in 30 seconds each.

How are you doing that? There are some things you can filter on, like brand, that come close, but not specifically "no third parties".

Edit: Answered my own question. You can find a place to restrict seller to "amazon.com". It's not 100% useful for all searches though, as you filter out sellers like "Apple", or "Bose". Would be nice if you could filter seller down to "Manufacturer or Amazon.com" in some easy way.

TweetDeck for Amazon: I See A Great Need.