The only side effect this will have is that it will push more people into buying Prime. Great comments in the other Amazon thread about how they're really playing the long game [1].
Personally, I think Prime is a serious USP for Amazon that is often overlooked. It's pretty controversial among analysts (from what I understand) with some claiming it's causing explosive growth [2] yet with others unconvinced it's sustainable [3].
Definitely a company to watch over the next 10+ years though...