Check this out:Obama’s People Turn To EU Bank For Inspirationhttp://www.independent.co.uk/news/business/news/obamas-team-turn-to-eu-bank-for-inspiration-1514983.html
Looks like potrace + colour quantization. Inkscape.org or Illustrator can do this and much more.
Sure but Illustrator also costs $1500. I got a cheap version before I left college but am now several versions behind the new 4 that just came out. It's just a fun and easy way to do it.
inkscape is free :)