In Canada, iTunes cards purchased for use on the iTunes.ca site cannot be used to purchase iPod/iPhone apps. You can purchase music, but not the apps. When one unhappy consumer complained to iTunes that she didn't want songs, she wanted apps, she received a quick response from iTunes. They offered her 5 extra songs. Obviously, they don't read their complaints, they just cough up additional music in response.

This Christmas: don't buy anyone an iTunes card.