An example was provided regarding the importance of having access to the source code. A game of scissors, paper, rock is implemented twice. The first time, the user and computer seem to have about an even chance of winning. However, the second time, using a game with source code hidden, the user invariably loses over a long period. This is because the computer cheats. But without the source code handy (it was supplied in a separate location), it's hard to know exactly what's going on.

Daniel