During DreamHack, which ended today, the Swedish Tax office (or Skatteverket) had a booth at the event as they wanted to inform the players attending DreamHack that they're obliged by law to pay tax on any money they make from winning gaming tournaments or from any kind of online sources.
The show is Scandinavia's biggest event for gamers and it's held in Jönköping twice a year. Skattverket posted a press release on its Website stating, "The Internet is not a tax-free zone and money made from playing games online need to be declared as income. It doesn't matter that it's your hobby. You've made a performance that you've been paid for, just like any ordinary job."
Of course, they're not just talking about professional gamers, but they're also trying to tax people that make money from online gambling, advertising on a blog, affiliations and, of course, sold goods, be it actual goods or virtual goods in say Second Life.
We doubt that Sweden is the only country trying to tax people on money they make online, but it'll be hard for the tax man to find every little penny that people make online these days; but be careful so you don't get hit with a huge tax bill once you've already spent all that Internet- made cash you didn't pay tax on.
More here in Swedish.