From the CTO perspective choosing a niche language is considered a much bigger risk because when your lead developer gets bored and quits you then have to scramble to find another lead dev who can quickly grab the reigns and continue. I've talked to many a CTO who have mandated PHP for exactly this reason, because you can throw a rock and hit a dev who knows PHP.
Oh, a snide question deserves an equally snide answer. =)
Probably better than finding a good dev in other languages for web development considering all the good PHP developers are still using PHP, and all the ones that couldn't cut it went on to learn the next LotM.
Honest answer: The same chance of hitting a good dev regardless of the language.
Unless you're Werner Vogels, in which case you mandate whatever the implementation team feels like using, as long as it scales and adheres to the service interface specifications.
I've heard Werner Vogels talk about this subject before. He chose Ruby for one of their projects specifically because they wanted very fast iterations, even though they new it wouldn't scale and they would have technical debt down the line. I don't think you are accurately describing how Amazon does things.
