In order to continue to be eligible for discounts at Amazon, users need
to at least use A9 once per week (eligibility criteria might change)
and you need to sign in before using the search engine (otherwise how
will they know that you were using the search engine)
No other search engine that I know of requires a login before
searching. No other big-name search engine pays their users either. By
offering a powerful incentive (money!) Amazon is getting users to
reveal what they are looking for using the search engine and I am sure
ultimately this information will be used to present the right set of
products while they are browsing at Amazon. Neat!!
There is an innovation war going on between Google and Amazon and hats
off to both companies for setting higher standards for each other and
every other company in that space.