Here is what WikiPedia has to say about accents:

Children are able to take on accents at a fast rate; children of traveling families can change their accents within a short period of time. However after maturity the accent we have is fixed and though it may have influences, or grow diluted it usually stays the same regardless of time. Accents can be expected to change until we are in our early twenties.

However, I have a friend in his mid twenties who has developed a cali-forn-i-a accent in a little over 2 months! The funny thing is, when we speak to him on the phone he speaks in his usual Australian accent! Is this really possible? Is he just pulling the wool over our eyes? Has he really become a biaccexual???? (Yes, I do believe I just made up a new word!)