Is Knime able to capture location coordinates from twitter/facebook webpages in order to visualize it through 'Open Street Map' map?
For instance, NVivo captures full twitter/facebook dataset, which includes location: http://www.youtube.com/watch?v=cuS40hHAw4w
you might want to have a look at the Palladian-Extension provided by the community. I'm not familiar with this project but I would check the "WebSearcher" first. For further question maybe the KNIME-Palladian-Forum is a good resource.
If you then get stuck visualizing your location coordinates, I'll be happy to help you.