Based on the IGDA's concerns, it's pretty easy to understand why they aren't encouraging developers to work with Amazon.
Amazon's new Android App Store has been drawing a lot of criticism, thanks to how the site's distribution terms and profit sharing requirements work. However, the International Game Developers Association has finally thrown its hat into the ring and unveiled some serious concerns about the new digital store, advising developers to educate themselves before they start submitting content to Amazon.
The IGDA's primary concern is that Amazon reserves the right to control games' prices. Not only that, but:
"Amazon reserves the right to control the price of your games, as well as the right to pay you 'the greater of 70% of the purchase price or 20% of the List Price.' While many other retailers, both physical and digital, also exert control over the price of products in their markets, we are not aware of any other retailer having a formal policy of paying a supplier just 20% of the supplier's minimum list price without the supplier's permission."
On top of this, the IGDA outlines five scenarios that developers will probably encounter at some point if they submit content to Amazon:
1. "Amazon steeply discounts a large chunk of its Appstore catalog (imagine: 'our top 100-rated games are all 75% off!')."
2. Be forced by Amazon never to give other merchants an exclusive promotional window.
3. Other distributors might feel obligated to duplicate Amazon's terms.
4. Amazon might steeply discount a niche title (or even make it free), thereby depriving the developer of a lot of money.
5. Amazon might also discount a top-selling title.
The IGDA's concerns seem pretty legit. As a result, it's not terribly surprising that the group has stated that it can't bring itself to endorse the site's store. The IGDA also stated that it formally expressed its concerns to Amazon, and Amazon has no interest in changing its terms.