This topic keeps coming up in the news, and I've altered my shopping habits because of it. The competition has gotten tougher with Google Express, Walmart delivery and pickup, Target pickup, etc. When I order from one of them or make a trip to the store, I can at least verify the item I'm purchasing is from the manufacturer.
When looking at the reviews on Amazon, countless times I've seen reviewers mention to not buy the item from a particular seller because it was not genuine or was defective. If I'm not sure about the brand, I'll search it to see if its legitimate and if there are reviews/complaints on other sites. I'll also use buying guides when determining what to buy instead of Amazon reviews.