Presumably by having a list of different technologies they are taking the approach of right tool for the job. The obvious side affect also being that engineers who work on this need to be polyglot as opposed to any specific tech. I certainly categorise this as a good thing, a developer and as a stakeholder (UK resident and user of the site).
Actually they're using the wrong tools for the job because they're having to rewrite bits regularly in different tech. There is obviously no evaluation taking place.
Establishing technical standards and homogenity is important on projects of this scale.
I think they established the reasons for it fairly well in the blog post, and even better in the comments elsewhere. I'd say they are the right tools for the job.
Maybe. Maybe not. The proof is in the pudding. It's immeasautably better than before and is a lot cheaper to run. Until otherwise I am of the opinion that they are making the right decisions.
