The discussion of XORing brings up two important points. The first is that, surprisingly, even an operation as simple as XOR can be used to create the strongest type of encryption known, provided that the key used is completely random and is equal (or longer) in length to the data stream to be encrypted. How you come up with completely random numbers is another matter entirely—whole books can, and have been, written on that subject.
The second point is that combining two or more techniques can result in a much stronger resulting algorithm. Taking this point up at a different level, consider how a system that assigns memorable but unpredictable passwords (or keys) has a significant edge over a system that assigns very difficult to remember passwords. In the latter case, it is human nature that a certain number of people will inevitably write down their password on a slip of paper and perhaps even tape it to their monitor!
As a different example on the same theme, consider the advantage one type of encrypted e-mail has over another type. One was written using couched phrases or only implicitly conveys a message. The other states its content in plain language. The first one stands a good chance of remaining confidential even if the encryption is broken, whereas the second message is cracked at the same time its encryption is breached. This illustrates again how multiple levels, particularly different types of levels, can combine synergistically to achieve a more secure result.