Let's talk about Google, then. In addition to having special ways of displaying results for different types of searches (local, geo, weather, shopping, etc.), there are also a
lot of different heuristics underlying the search results. It's not just PageRank-and-done, it's many different approaches trying to maintain a uniform level of quality across a variety of niches.
I'll repeat that again: it's not the approach that's homogeneous, it's the quality.
You can see this with Apple, too. Their devices aren't limited to some set number of use-cases, it provides an API and ecosystem for creating new, domain-specific applications. You mention Objective-C in your response, which is kind of missing the point; we're talking about domain-specific applications, not domain-specific languages. LightTable will presumably be very consistent and general at the API level, and uses Clojure, which is a general-purpose language as well.
As for Amazon, their offerings span the entire spectrum from general to domain-specific. You can get an empty VM, but you can also get something like Elastic MapReduce. Amazon will happily develop domain-specific products on top of their platform as long as there's a large enough market.
Finally, look at Rails, which is a framework specifically for creating web apps. It doesn't help me write a new NoSQL server, it doesn't help me write a new AAA video game, it seems to be doing okay all the same. It's used because it's a really effective lever in certain, specific cases. If we can have a development environment which is a similarly large lever across a wide range of cases, how could that ever be a bad thing?
