The blog phenomenon can be analysed from various angles. This article considers it from an economic point of view, to establish whether blogs are a profitable market. Blogs require the use of platforms which store and allow the consultation of content put on line by bloggers. These platforms have operating costs, which means that the survival of blogs depends on their profitability. This article analyses the functioning of the market and shows the coexistence of private individuals' blogs, based on a free-of-charge model (large number of advertisements), and professional blogs based on a pay model. At this stage none of the platforms are profitable but the chances of them soon becoming so are very high.