I wanted to address one issue specifically since I still think people have a weak grasp of what it means.  That issue is scaling.  There have been two scale arguments that have been presented to me in the responses to my last post so I addressed both below. 

Scaling for an Individual Application

One of the arguments presented has been that Google's solution allows applications to scale beyond the point that a shared host could match.  This is because, according to those who make the argument, Google has massive resources that they can employ if your application grows into a high traffic site.

What people are missing here is that, once you get to a certain size, it becomes cost effective to host your own site.  No matter how efficient a company like Amazon or Google is they have to charge an overhead to make money.  Once you get to the point where you can afford to hire a full time server person and maintain a server farm for yourself there's no way those companies can compete because of the overhead they have to charge. 

So people thinking that one of the benefits of the Google App Engine is that it can scale into infinity miss the point that no one will ever need that even if Google was providing it. 

Which Google isn't, and that brings me to my second point...

Scaling for Multiple Applications on Google's Server

There's been much confusion over one thing in my previous post.  That thing was...

Google App Engine's ability to scale depends on how much server resources Google is willing to dedicate to the task of running these applications.  Google is not going to risk slowing down their primary services for a Google App Engine application.  So their ability to scale could very well be less than other companies, we just don't know.

So I thought I'd elaborate on that.   One of the arguments people have made is that Google's massive data centers gives them the capability to completely eliminate performance drags.  So Google App Engine applications will perform faster because they'll never have to wait for CPU resources. 

What this line of reasoning misses is that we don't know how many of Google's computers they are willing to dedicate to the task of hosting App Engine Applications.  So while a normal shared host might put 100 website's on every computer that still might outperform Google if Google's Server-To-Application ratio is higher.  So even if Google has 300,000 computers dedicated to Google App Engine and your shared host only has 100 computers to their name they could very well be even in performance if Google has 30,000,000 App Engine applications to run. 

In fact, I'd argue that Google's popularity and the fact that the service is free makes App Engine more likely to exceed your average web hosts Server-To-Application ratio. 

In the End...

When all is said and done my point still stands.  Scalability really doesn't play a part when deciding between a web host and a service like Google or Amazon.  It all boils down to price.  Since Google has chosen not to reveal their pricing yet there's no way to compare.  That is exactly why it is too early to be singing the praises of Google's solution (which was the point of my last post).