Phillipson's Linguistic Imperialism is an important book and I doubt that any serious discussion of English as a World Language should avoid a discussion of his work. Linguistic Imperialism raises the point (all too often disregarded) that English Language Teaching doesn't happen in thin air, that it is connected with politics and ecconomy.
Phillipson argues that the center (that is the English speaking countries of the West) have used English to supress the people of the former colonies. This phenomenon he refers to as "linguistic imperialism". He deals with 5 tenets,or rather fallacies, which have been used for such imperialistic purposes; the most important of these fallacies are that English is best taught monolingually (without using other languages) and that it is best taught by a native speaker.
While Phillipson raises many interesting points (the fallacies of ELT among them) his overall thesis has to be rejected on the following grounds (to name but a few):
on its in-built power asymmetry, that is that the devloping countries are seen as being incapable of independent decisions.
that fact that linguistic imperialism is not falsifiable: there is no scenario where Phillipson would admit that English DOES fulfill a useful role in a third world country.
Phillipson's left-wing terminology and tone: imperialism itself is a left-wing term.
a country's linguistic ecology is to complex to fit into Phillipson's neat "black and white" scenario.
Phillipon's book can thus be only a start for a discussion on global English. For further reading I recommend Kachru's "The Alchemy of English", Crystals "English as an International Language" (critical reading necessary) and Pennycook's "The Cultural Politics of English as an International Language."