I agree that amazon suggestions are not great, but Amazon have a fairly limited set of information to go by - only your previous purchase and search history on that site. If Amazon had the same amount of information that Google/Facebook has, they would be able to make much better recommendations.
As an aside, Amazon should really have an 'I already bought this somewhere else' button. 6 months after searching on Amazon for a watch but then buying it elsewhere, I'm still getting watch suggestions...
I really think that we are in a period of fundamental change regarding information. The norm has been that we find information, but increasingly information is finding us.
While I don't feel the technology is quite there yet, it's only a matter of time before recommendation/predictive systems reach a level where they are able to personalise everything that we interact with.
As an aside, Amazon should really have an 'I already bought this somewhere else' button. 6 months after searching on Amazon for a watch but then buying it elsewhere, I'm still getting watch suggestions...