In reply to Neverfly, see Original Post: "I'm a little confused... The references you gave did not answer your question?
Barred Spirals are a product of galactic evolution. Essentially, a spiral galaxy should grow a bar given time.
The bar is formed due to the immense gravity of the spiral hub. As stars move in their orbits, instability eventually leads to elliptical orbits. As more and more stars develop elliptical orbits, the bar becomes more pronounced.
The Milky Way will lose it's bar spiral status in about 5 billion years."