The root of the problem is a lack of space in the Amazon warehouses. Amazon themselves is selling more then they ever have in the past and every year there are more and more FBA sellers shipping thousands and thousands of items into Amazon warehouses. Fees going up are inevitable however the lack of space has caused Amazon to make some drastic changes. Amazon has raised storage fees, changed the way long term storage fees are applied and changed the fees book sellers pay for each item sold through FBA.
In my opinion, long tail items are whats killing the profitability of FBA. It is one thing to buy an item that turns long tail because of factors outside of your control but its another thing to build a business model around long tail items.
Why are long tail items so bad for Amazon and all FBA sellers? Check out the video below.