Essentially amazon are giving the power of a database to people used to excel and simple queries, backed by their massively optimised infrastructure. It will make popping up a web shop even more trivial than it has been in the past, and i guess continues along the growing trend of allowing "content to be king". i.e. u dont need a sql geek in your corner, just a good idea .
Now this will obviously work only for simple queries in the short term, but it is a big score for a pay per use hosted db service. It obviously raises privacy questions but this is a trade off im sure many will happily make..
(it also raises the interesting question of sabotaging someone, by simply running multiple queries on his site.. i.e. since the site owner is paying amazon based on db usage, a simple wget script that fetches the price of an item recursively could end up costing the site owner a small fortune! Now this is a similar problem to the one google had with ad-words, but ad-words self regulate based on pricing.. i.e. if i have an ad and am willing to pay $1 per impression today i am happy because i have calculated that i get an x% conversion. Some monkey wgets my add 9999999999999 times effectively uppign my cost of the advert.. but.. this also affects my value.. because my conversion rate just went down.. so i will be willing to pay less for the ad.. the db usage cost (from the little ive seen) is fixed.. which means it costs me, but never amazon.. (in an extreme, it would pay amazon to hire ppl to surf apps that are hosted through simple DB) ;>)
Thats just me the pessimist speaking.. for now.. its cool, and bears watching!