I really think that this is the big plus for Google's app engine. Most web sites are essentially front end GUI's for a database with a sprinkle of data crunching thrown on top. It's all about the database. And, one of the biggest pain points for a growing startup is scaling the database.
Enter App Engine. Google has spent years developing Big Table and their underlying distributed OS, and they are probably years ahead of anybody else on this one. Essentially what App Engine consists of is giving 10,000 developers read/write accounts to the worlds largest distributed database management system.
Now, it's up to the developers to add their HTML/CSS/Javascript GUI's and a little data crunching middle-ware all the world to use.
One is that Google's DB is both unique and closed-source. Worse, it isn't even a product like Oracle or SQL Server that I can license and then use the way I want. Even if I wanted to buy the hardware and maintain the software, I can't move my app off of Google. I'm a sharecropper. They get my traffic data for free, and if they change their pricing structure or the way their DB works I have to scramble to keep up. And if they decide to screw with me (like, ahem, becoming my competitor) I will have to port my app to some other scalable platform while serving all my accumulated traffic and simultaneously fending off a deep-pocketed competitor.
I'm also suspicious of the idea that BigTable is some sort of magic wand that solves any and all scalability problems. I'm very sure that BigTable scales for the classes of problems that it was designed for. And I'm sure that a wizard like Steve Yegge or Peter Norvig can adapt it to many other classes of problem. But, without actually knowing anything about BigTable, I'm prepared to bet that using it to scale your web app will require (a) knowing a fair bit about how the tool works and (b) customizing your app's data storage scheme to compliment the tool, after which (c) there will still be some corner cases that don't work very well and require clever hacks and compromises.
In other words: I predict that in three years there will be Craigslist job postings for "BigTable DBA with five years of experience".
Enter App Engine. Google has spent years developing Big Table and their underlying distributed OS, and they are probably years ahead of anybody else on this one. Essentially what App Engine consists of is giving 10,000 developers read/write accounts to the worlds largest distributed database management system.
Now, it's up to the developers to add their HTML/CSS/Javascript GUI's and a little data crunching middle-ware all the world to use.