This blog post was written after an inquiry about Amazon's EC2 and S3 services, but it applies much more generally to anyone trying to run a business and depending on an outside service provider. LJ comes to mind, for example. Amazon's terms and conditions include the following disturbing paragraph, which I suspect is not at all unusual in such places:

We further reserve the right to discontinue Amazon Web Services, any Services, or any portion or feature thereof for any reason and at any time in our sole discretion. Upon any termination or notice of any discontinuance, you must immediately stop your use of the applicable Service(s), and delete all Amazon Properties in your possession or control (including from your Application and your servers). Sections 3, 5, 8 - 12, any definitions that are necessary to give effect to the foregoing provisions, and any payment obligations will survive any termination of this Agreement and will continue to bind you and us in accordance with their terms.

In other words, we can pull the plug on you at any time, on no notice at all, but you still have to pay us if you owe us any money.

Think about your web hosting service, your ISP, your online banking, web email provider, your web storefront provider, your blogging service (gestures toward SixApart),... Which of them have real SLA's (that's Service Level Agreements for us Luddites) and which have terms like Amazon's?

Now: which of them is your business depending on, and what are your disaster plans if they suddenly go belly-up, get taken out by the local flavor of natural disaster, or simply get distracted by the next shiny bubble-of-the-year and decide they don't want to play anymore?

Now, if you'll excuse me, I have to do some serious planning.