I suspect it'd be more problematic in for instance Japan, Korea or China.
Linguist David Crystal, who has surveyed world use of one or another "interlanguage" for official use by international organizations, has found that actually most frequent and most exclusive use of English as an interlanguage is in east Asia. It is remarkably "natural" for a Korean person to try speaking English to a Japanese person (even though Korean and Japanese are cognate languages), and it is more expected still for a Chinese person to speak with either of them in English. What I find remarkable, but have observed more than once, is speakers of different Sinitic languages ("Chinese dialects") speaking to one another in English. Online, which is mostly the context Jeff is talking about in his blog, the early inconvenience of typing in the CJK languages (now resolved, as an in-country issue, but still a big barrier to switching among those languages) resulted in much Internet communication in east Asia being in English by default.
After edit: France was mentioned in the reply above to which I reply here, and I'll mention that the Carrefour retail chain has stores in Taiwan, and the signs inside the stores are in Chinese, of course, but also in English, NOT in French. There is no reason of national pride among the Carrefour staff sufficient to overcome the practicality of using English to reach customers in Taiwan. (Taiwan has a large population of English-speaking foreigners, the plurality of whom are Philippine guest workers.)
Is that most frequent per capita or total occurrences?
At least with the limited contact I've had with Chinese and Japanese developers the level of English wasn't particularly high, so I guess I'm a bit surprised by that. In the Chinese teams they even went as far as to try to suck in someone from Hong Kong so that he could be the bridge between the Chinese and German (the team I was on, though communicating in English) groups.
Replying to your reply to my reply to you, my main point is that if a Korean is with a Japanese person, they MIGHT speak Japanese (I have seen that happen), or they might speak Korean (I have seen that happen more rarely), but most likely they would speak English with each other. Add a Chinese person or a Thai to the conversation, and it is overwhelmingly likely that they will all be speaking English to one another. The standard of spoken English varies from one country to another in east Asia. One problem is that many of the better English speakers eventually emigrate. But English is the general language of intercommunication among people from Asian countries, for lack of any other language in which speakers have stronger proficiency that they all speak.
Your observations on English as an "interlanguage" is interesting. I can see this happening.
As to the observation of different Chinese dialects using English as an interlanguage within China (...I assume you didn't mean within China)...this is probably very rare. In my 9 years of living in China mingling with all sorts of regional and ethnic groups, I have never once seen this happen.
English as an interlanguage among Chinese people has become much rarer since the retrocession of Hong Kong strongly promoted the use of Mandarin there. Most of the examples I had in mind date from the era when an educated Hong Konger would be much more likely to speak English well than to speak Mandarin at all.
It might have something to do with the installed base of the language, so to say. Large languages like French, German, Japanese and Chinese may have an expectation that people should learn their language.
Small countries like Iceland, the Netherlands and Denmark can't possibly expect anyone to learn their petty language that can't be used anywhere else, and thus realise that they have to learn English if they want to communicate outside their borders.
I think it's that plus literary tradition. The Netherlands isn't actually that small population-wise, but it has a long tradition of its best minds (e.g. Spinoza, Erasmus) writing in the lingua franca of the day. Even though there are only four times as many people in France as the Netherlands, I'd guess there's more than twenty times as much written and published in French.
Edit: Interesting note -- if Dutch, Flemish and Afrikaans are all considered the same language, then Dutch has around 30 million native speakers.
Interesting and valid point, but I think it only applies to some countries. Søren Kierkegaard, Niels Bohr and Hans Christian Andersen all wrote in Danish (to my knowledge at least) and the Icelandic Sagas were written in Icelandic. So a portion of small countries that have good English skills don't seem to have that tradition.
I'm a french living oversea and so write and think mostly in english... Most of my friends in France work in french and their english level is often quite weak (especially when it comes to oral communication, one of my teacher at university used to read 'done' as do-one, case as 'cahse' and so on, it was rather funny...)
When working in japan, none of my japanese coworkers could speak or read english (even worth than France...) and they only read translated programming books with a 6-12 month latency to get new information....
Now if I hired programmers, I would never hire someone who doesn't read english fluently because I believe that someone, who is truly interested in programming, will try hard to learn English so he can access to the quantity of knowledge written in English.
French was an 'imperialistic' language as well, until not so long ago; France had a strong economic and diplomatic influence. You had good conferences in several domains in French. It's tough to loose this kind of influence, and I think the case is similar for countries like Japan or Italy. Young people in e.g. Poland seem to have it easier to adapt...
But your last sentence seems really harsh. Good communication skills are so much more important in real life to have work done.... I know a few good programmers in France for whom reading english is a lot of (sometimes necessary) pain. I'm sure more contacts with foreigners would give them a incredible confidence/motivation boost.
Even here in Italy, which doesn't have a strong tradition of using English, most programmers use it (although I am currently working on a Rails contract where all the models have been translated into Italian, with the accompanying pain that that brings...)
