John loves Wikipedia, and so do I. John got reminded about his love while looking up European Union in Wikipedia. I followed the link, and started to think "wait, EU is not Europe. Europe is actually much larger than just EU!". Then I looked up the Europe article, fell in awe while reading the population density table (from 2.7 person per square km in Iceland to 16403 in Monaco!). But the information I was actually looking is related to the various languages spoken in Europe. A picture being worth a thousand words, here it is:

Source: languages of Europe (hi-res PNG), on Wikimedia Commons

See how diverse Europe is in terms of language[1]? If you click to see the larger version with its legend, you'll notice that national borders do not strickly follow language borders... But to get you mind totally blown up, go and try to read the super-long list of languages in Europe.

Now you can imagine how hard it is to do things like community work and public relations when communication is difficult... But at the same time, product localisation and website localisation are a must for Firefox and Thunderbird to strive in such a complex environment, and thanks to local communities, they are wonderfully executed and made available to the world, while commercial competitors often find no economic incentive to cover so many languages...

Notes

[1] And don't get me started on its 48 countries and 29 currencies!