These days nothing is safe unless its tied down and even then it might not be safe from thieves. A popular item to steal these days is your bike and frankly, thee isn't much you can do to stop theft of a bike. You can chain it securely to a wall, remove the wheels, handle bars and so forth but if someone is gonna steal it then they will.

Recently, I parked my bike outside of a store while I was doing a spot of shopping. Now I am a big believer in security so I chained both wheels to the wall. There.... that should do it I thought as I disappeared into the store...

Well, obviously not enough security...

Here is my bike....

Nice!