Gothenburg and Facebook - what's up?

I just had a quick look at the regional/local statistics for Facebook in Sweden. To my surprise Gothenburg seems really underrepresented.And yes - I also used Gothenburg (and even Goteburg) as search terms - all gave a similar figure.

As a comparison - the same search for Stockholm returns more than 2.6 million people (far more than the official population in the region?) and for Malmö it returns 234 000 people.

The official population of Gothenburg is just above 500 000 individuals (Gothenburg is the 2nd largest city in Sweden).

How come? Any ideas? Could it be that:

• People in Gothenburg doesn't use Facebook and social networking sites to a large extent?
  
  
• Perhaps there's another social networking site which is large in Gothenburg?
  
  
• People in Gothenburg would rather not state that they live in Gothenburg?
  
  
• A slightly more technical possibility - Facebook uses, among other things, the user's IP address to decide the geographical location. Perhaps the Internet connections in Gothenburg are routed through Stockholm or some other place?

I'm stumped and surprised. What do you say? Do you have any Facebook friends from Gothenburg to ask..?