abstract: We will discuss motivation for and approaches to the question of when the monoid in the mapping class group of a surface with boundary corresponding to monodromies of open book decompositions of Stein fillable contact 3-manifolds differs from the monoid of mapping classes which admit factorizations into positive Dehn twists. In particular, combining new results with previous work of several people, we give a complete solution to this problem, showing that the monoids coincide only for planar surfaces. This is joint work with Vitalijs Brejevs.