From the FAQ :
"At launch AWS Lambda supports code written in Node.js (JavaScript). Your code can include existing Node.js libraries, even native ones."
so it seems that you can avoid lock-in if most of your javascript code is not too coupled to Amazon's API
And they claim on the detail page:
"With AWS Lambda, there are no new languages, tools, or frameworks to learn. You can use any third party library, even native ones. At launch, AWS Lambda will support Node.js code, with support for other languages coming in the future."
Anyway, libcloud seems to be leading the way in this kind of standardization, so that's good news. There's also providers that have drop in AWS-compatible APIs for some services. Then there is stuff like apache mesos for creating that infrastructure, which is less relevant to smaller companies.
But I suspect that the last thing Amazon wants is to turn into a commodity, so it's in their interest to release as many differentiators with non-standard APIs as they can.
It seems that this system puts together all events generated by Amazon services to trigger new events. This is usually not that complicated to code, but the catch is to make these (usually) scripts/programs highly available, which Amazon provides.