The multiplication of magnetic domain walls under the effect of induced currents developed during high frequency magnetization loops is experimentally investigated in ultra-soft nanocristalline alloys in order to determine the effective anisotropy and to check the predictions of the Random Anisotropy Model used to explain their extreme softness. For the first time, direct observation of multiplication is achieved and resulting effective anisotropy determinations underline the importance of induced anisotropy upon effective anisotropy.