While Dark Matter theory attempts to find an underlying mechanism that would predict the high velocities of stars in the outer rim of galaxies, MOND simply curve fits the observed fact with a new formula for gravitational force.

MOND

I should point out that galaxies at extreme distances also seem to have very high velocities, as suggested by doppler redshift of atomic spectra and time dilation of supernova events. The Big Bang Theory which leads to a causality violation (an effect without a cause), and Cold Dark Matter which seems untestable, both might have the same underlying mechanism. This is my own theory-of-the-moment. Whoever solves one will solve the other, I think.