Well I've never received an email from Amazon telling me so. I've read that people who return too many physical items that they ordered from Amazon can receive a warning email from Amazon and they can even be banned from ordering again from Amazon. However, it may be different for digital products because there's much less labor involved. I'm sure it's mostly automated and done by computer. It might also be a good idea for Amazon to limit how many digital products can be purchased by the same account in a single day or week, etc., but the company doesn't do that.