Open data is seen as a promising source of new business, especially in the SME sector, in the form of new products, services and innovative solutions. High importance is seen also in fostering citizens' participation in political and social life and increasing the transparency of public authorities. The forerunners of the open data movement in the public sector are the USA and the UK, which started to open their public data resources in 2009. The first European Union open data related directive was drawn up as early as 2003; however progress in putting the idea into practice has been slow and adoptions by the wider member states are placed in the early 2010s. The beneficial use of open data in real applications has progressed hand in hand with the improvement of other ICT-related technologies. The (raw) data itself has no high value. The economic value comes from a balanced combination of high quality open (data) resources combined with the related value chain. This paper builds up a "big picture" of the role of open data in current society. The approach is analytical and it clarifies the topic from the viewpoints of both opportunities and challenges. The paper covers both general aspects related to open data and results of the research and regional development project conducted by the authors.