My first programming language (ND80) saved all identifiers by reference in order to save RAM, which was scarce. Using the swap instruction, it was possible to replace any identifier with another, so basically, the entire, programming language could be translated to Danish, my native language. Sounds ridiculous, right? It was. Later, Microsoft did the same: Excel functions were translated to Danish, and even VB programming was Danish-ified, COM APIs were localized etc. This caused a huge amount of problems - it made support difficult, it made it difficult to find help on the internet, localizing APIs meant that some apps did not work with MS programs that were localized to other languages etc. Of course there were workarounds and solutions for most of the "problems", but the problems were real and sometimes caused real havoc. One of the 5 Danish regional administrations just introduced ODF as standard format for document interchange between MS Office 2003, MS Office 2007 and OpenOffice, because this solves problems like date format problems (ddmmyy in some, localized ddmmåå in others). It will not be solved fully, because if you have an expression in a spreadsheet where 'ddmmåå' is part of it, it may not work in a non-Danish spreadsheet at all, no matter how you save it. The easy solution was to do everything in English, using U.S. notation (decimal dot instead of decimal comma) etc. I guess everybody now realized that this is the way to go for source code, APIs, XML files etc.
However, in the recent years, evolutions in the internet has expanded this problem. Humans are increasingly interfacing directly to software, specifying parameters. The most common interface is the search engine. How do you explain it easily to a 6 y.o. how the angle of Earth's rotation axis creates summer and winter? Youtube, of course. But don't use Danish words for your search, it will probably not yield a single good result. So, even though my daughter can write on a computer, she still cannot use youtube. She doesn't know English. I encounter this problem many times per week.
The problem is not just limited to searching. Many electronic devices are not localized, a lot of software is not localized, and what language do you use on Facebook if your friends don't all understand Danish? Wikipedia is another good example: The absolutely biggest wikipedia uses the English language, and it is 3 times bigger than number 2: German. Wikipedia has become a significant provider of information, and you simply need to know English to use it.
In order to understand all implications of international contracts, English is the language of choice. EU has made a guide for European English, which defines a terminology that may not always match that of any English-speaking country, and many terminologies are translated from English-language originals. English has become the new Latin.
Google Translate tries to solve some of this. However, when I read Chinese web pages in Danish, using Google Translate, it is obvious that it was translated to English before it was translated to Danish. There can be many reasons for this, but it surely helps comprehensibility when I use Chinese->English instead of Chinese->Danish. Anyway, Google Translate cannot solve all problems, it's merely a patch.
Only 1-2 decades ago, you would have looked at the size of countries, measured by population count and economic size, in order to find out what language to learn. Today, English is much larger than the sum of English-speaking countries.
The latest statistics indicate, that other languages than English are currently losing popularity in school in Denmark. That's a problem: Most people in the world don't do English well. If you want to target those people, you need to localize. Even when you meet a person that seems to talk and understand English well, you need to realize, that this sometimes requires the full brainpower of that person. In other words, if you ask this person to solve a complicated task, that involves the use of English language, like programming HD recorder, it is much harder than if the HD recorder had been localized. Also, just because a person knows how to express himself/herself in English in a given context, it doesn't necessarily mean that this person can express himself/herself in another context that would work out fine in his/her native language. In order to localize well, an application specialist should know the target language well enough to be able to inspect the localized result.
So, remember to localize, learn languages, and remember to teach your children English. And in the unlikely case that your native language is English, here is a sign not to laugh at, it's very serious:
If you're in doubt about what it means, use Google Translate.