The Fila Brasileiro (Brazilian Mastiff) is NOT a dog for most people. They are also considered a rare breed and aren't largely available - something that reputable, responsible Fila people try to maintain. They are only for very experienced dog owners who are very at ease with dominant, self-determined dogs that need a great amount of socialization and time with their owners.
Here are some links that will tell you more. The first is a thread here with a description of the Fila's temperament. My Fila-expert friends thought it described it very well. The other two links are to a very informative site built by a true expert on the Fila, and the breeder my Kharma came from.
http://www.chazhound.com/forums/showthread.php?t=799
http://www.mindspring.com/~anableps/fila.html
www.defenderfilas.com
There are some European countries that have banned the breed or severely restricted it, and I believe I remember being told that Australia - or parts of it - have banned the breed as well. They tend to be very misunderstood. They are a working breed and are perfectly suited for what they do. We actually use ours with cattle, as they were bred to do centuries ago in South America. If well and carefully socialized, they can make excellent companion animals, and have been used in enforcement, rescue, "sniffing," and other types of work.
But I can't state strongly enough that this is definitely NOT a breed for most. They also tend to take over your life and you become addicted quite easily, and you will never leave the house again without some sort of doggie print on your clothes . . .