Ah. In a way, that's almost like MagiTek in FFVI - forced extraction of Esper powers isn't as useful as converting them to Magicite...

I remember that bit in the Junon's Beginner Room too... haha.

But then I guess the question remains: Is the materia you use Shinra materia or naturally occuring materia? I guess all the materia you can buy is made Shinra-style, whereas everything else (summons esp.) is natural...