Google this week began a limited beta test of its new Google App Engine, a platform for developing and running Web applications. Its arrival into the infrastructure-as-a-service space will surely not go unnoticed by Amazon.com, which appears to be building a significant business selling computing power by the drink through Amazon Web services.

Google's arrival on the scene offers developers the chance to test out Google's vaunted infrastructure for themselves. Much has been made of the competitive advantage Google enjoys because of its ability to deploy and link commodity hardware to form a superfast, redundant network. It will be interesting to see whether there's substance to the mystique, or whether Amazon, as its people have claimed, runs an equally impressive, though less storied, IT operation.

It's probably only a matter of time before Microsoft gets into the act. Microsoft, after all, has been shadowing Google's moves for a while now, and it's hard to image that the hypercompetitive Steve Ballmer wants to cede the cloud computing platform space to Amazon, Google, and a few plucky startups.

And that's great news for developers. With so many options emerging, deploying online applications has never been easier.

But developers looking to travel the path of least resistance should pay close attention to the risks of depending on someone else and to the limitations imposed by terms-of-service contracts. We're talking about outsourcing your infrastructure, after all.

Google embraced open source software as a way to control its own destiny, without being subject to contractual hindrances. For startups that aim high, that want to compete with Google rather than be bought by it, there's still something to be said for building everything yourself.