I don't think that these petitions in Change.org holds any significance. Amazon is not legally bound to accept Bitcoin, even if the petition manages to get 10 million signatures (that said, the target of the current petition is just 5,000 signatures). Amazon is a private company, and they have the freedom to accept whatever payments they want. You can't force them to accept BTC, if they are not interested in it.
I think online petitions are useless in general. Getting Amazon to take bitcoin is a good thing, but this is the wrong way to go about it. People who are interested in that need to flood Amazon's corporate offices with letters and emails. They may come around eventually.