We have investigated the effect of large numbers of moderately sized spots placed randomly on a differentially rotating star as the explanation of the rotational light curves of magnetically active cool stars. This hypothesis produces light variation very similar to observed light curves of RS CVn binaries, provided there are of order 10-40 spots at any time and provided individual spots have a finite lifetime.
Eaton, J.A.; Henry, G.W.; Fekel, F.C. "Random Spots on Chromospherically Active Stars" Astrophysical Journal v.462, p.888 (1996)