Optimizing content is not difficult. Once you have a fair grasp of your targeted keywords, can write reasonably graceful copy incorporating identified search terms, can do so while abiding by the rules of keyword density and proximity, then it’s really rather simple. You should be in good shape to attract both man and machine. At least in your source language which, typically, means English.
But what happens once you take your carefully crafted text and decide to push it out for global consumption? You translate. Perhaps you localize which sometimes but not always means something more. And what of optimization? It appears to me that SEO has rewritten the rules of localization: incorporating unique cultural and linguistic nuance is no longer enough. Localization now has to take into account not a literal or even idiomatic translation of keywords but it must identify these in language and replace as needed. Keyword density and proximity can reshape syntax if one isn’t careful so the translator’s task is now (or should now be) more complicated.
As for what the major localization companies might be doing on this front? It appears they are yet to rethink the consequences of SEO in their arena.
I would venture that most translated sites that use US English source content are not optimized, not even for UK English. That the exercise of optimizing, typically left to the local, in-country, Web group rarely happens, and organic Search results ultimately languish.
What is the best way to handle this? Centralize all language content optimization or leave to country personnel? I tend towards the former. More on this later.