1) If the currently active application is supported by a Behaviour, 
that application is controlled.

2) If the currently active application is not directly supported via a 
Behaviour, but it can find an application running in the background 
that is supported by a Behaviour and which is flagged as "controllabel 
in the background", Remote Buddy controls that application.

3) If no Behaviour could be found in either 1) and 2), the Default 
Behaviour is used.

Background is this: most users don't want to have to make iTunes (or 
DVD Player, EyeTV, ..) the active application first before they can 
control it with the remote, even though no other controllable 
application is currently running.

If you want to always start in the main menu level instead of at the 
context menu level, you can achieve that nonetheless, by choosing the 
respective action for the menu button at Prefs > Mapping > Global 
Mapping.

Best regards, 
Felix Schwarz