Field, laboratory, and theoretical analyses of methane hydrate are in general agreement that the presence of methane hydrate in natural sediments changes the physical properties of the sediment. It is much less clear how and why these changes occur. Among the discrepancies and controversies that exist are if and how cementation occurs, what role grain size plays, temporal relations of formation, whether water saturation is significant, and whether it matters if hydrate forms from a dissolved phase (as inferred in the natural environment) or from a free-gas phase (as conducted in most laboratory experiments).