Under this potential tax treatment, someone using localbitcoins to sell bitcoins would be the equivalent of someone using blocket to sell a car, right?  My understanding is MOMS is charged for profits from sales on blocket only above 50.000 SEK (7,500 USD).  Only if you are a regular seller of something would you need to report to the tax authorities your yearly profit from person-to-person sales, and that profit would be taxed at a 30% rate. 

From Blocket.se:

     Sale of individual items

     If you sell goods on any single occasion, then the possible profit that exceeds SEK 50 000 is taxed at 30%.

     Profit is the difference between your purchase price for the goods and the price you then sell the item for. If you have received or inherited what you sell, it is the previous owner's purchase price you should count on. Do not you know the purchase price can make use of a standard value which is 25% of your selling price.