javascript - Is using Amazon s3 as a database (of sorts) for a PHP app a bad decision? -

i'm teaching myself javascript , php building app, , decided use amazon ec2 , s3 platform. question using s3 "database", i'll start bit of background.

the app uses class interact s3 buckets: http://undesigned.org.za/2007/10/22/amazon-s3-php-class/documentation#getobject

when user logs app, app download file s3 bucket. every user has own file. using json, bring data client side, , of "interaction" client side (using javascript) , bit of php. once user done (probably after 30 minutes or so), app save/upload , replace s3 file.

my reasoning behind of think app scalable. hope can use load balancing, each instance being able interact directly s3. if lots of users log on, can create lots of "micro" or "small" instances handle them all. 1 of drawbacks of ec2 if instance crashes or goes offline, data lost, thoughts instead of having - why not build app around s3 in first place?

my question: make sense? there reason haven't seen many examples of kind of thing "in real world"?

thank time!

cheers,

have seen amazon simpledb?

creating own datastore , storing on s3 doesn't sound practical, have upload , download file every 30 minuites, hardly sounds scalable me! if server goes down or file gets lost?

you can run mysql , other databases on amazon, why not (say daily) s3 instead.