The Roma, again

PRI's The World reported on efforts to reintegrate the Roma into Bulgarian society.  This link should get to an audio of the report.  The question remains/arises:  what is  it about Europe (east or west) or elsewhere that the Roma  create this tension and inability for one group to be accepted by another.  This situation has been intractable for over 1000 years. A second Wikipedia link has some interesting information on the arrival of Roma people in North America in the early 19th century.