Quite frankly, I don't know if that's true or not(1), however the relationship between lift and (induced) drag is not a constant factor - it depends upon the aerofoil.
For instance, if one takes a flat sheet, it will generate lift - but it will be somewhat inefficient at doing so - If you curve that sheet into an 'aerofoil' section, it will become somewhat more efficient at generating lift - the drag per unit of lift will be less.
Different aerofoil shapes will have a different lift/drag curve. When you start sticking out flaps, slats and suchlike, you change the aerofoil, and change it's L/d ratio.
(1) I'm don't think it's that useful to consider just the induced drag - it's only a small part of the picture, hanging flaps out dramatically increases the parasite drag. In any practical terms, you need to consider the combined effect of induced and parasite drag.
Last edited by Mark1234; 21st Oct 2008 at 23:56.