Thieves and pickpocketing are very common in Spain and in most of the touristic places all over the World. It has been reported that in the gay area, thieves work in groups of two or more. They pray on the drunk visitors by hugging them and being very friendly. While you feel happy you are talking to new people and hugging them, they are stealing your cell phone and your wallet. Even if you put your wallet and cell phone in the front pockets, you will not feel a thing. So be very aware of your belongings and your pockets.
One solution is to put a zipper inside the top of your pocket. Another solution is to have a money belt.