[unz]

Let's say you're a college student or career changer who just learned python. You can write a script, upload it, and have the world use it for free.

You then learn sql and build complex apps.

Learn about bigtable and build a viral app that scales to anything.

Learn golang and make your python code more efficient.

And you can do this all free to start off with.

The alternative - learn linux, web servers, db admin, security. Or php/mysql and pay shady hosters $20 a month and buy domain name.

If you're experienced and know all about servers etc, you can now ditch all that knowledge and outsource it to someone else and focus on higher value things.

[rbanffy]

It also encourages you to write scalable applications - no in-request long operations, queues, eventual consistency, no filesystem access dependencies, planning for failure on every level etc. Using App Engine is a course on best practices in web development.