How SimpleDB Differs from a RDBMS
highscalability.com
highscalability.com
It's kind of odd, but I've noticed that databases are a touchier subject than most things in the computer world. If someone says they're not using a RDBMS, there is always someone who immediately jumps down their throat as though SQL is God's Gift To The World.
Anyway, RDBMS aren't going to go away, so if you like them, use them. Some of us are willing to experiment with other solutions, however :)
It also makes for a scaling nightmare for startups who's #1 scaling issue is typically DB related.
In this respect traditional SQL is starting to show its age. My prediction is it will begin to become phased out for most web application purposes in favor of more easily scalable cloud-based and services such as SimpleDB and BigTable.
Besides, what's so nasty about SQL?
And you can still use SQL (albeit restricted) on SimpleDB with some of the new wrapper libraries such as this one: http://code.google.com/p/simplejpa/
But what happens with dynamic apps, when you need to update that data base as often as you need to read it? Don't pull the plug on your RDBMS just yet.