Do you consider nationalism a positive ideology?

In a quickly globalizing world, with rising multiculturalism and a great need for solidarity among people with divergent origins, nationalism seems to be more of an impediment. Future humans may look back and see nationalism as being a divisive force, rather than a source of pride. Why? Social capital needs to be generated on a global scale to bring about real change in the power structures that control this planet. Social capital that is based on nationality does not serve this end nearly as well.