There are two kinds of mergers: those between roughly orthogonal businesses that want to exploit some vague "synergies" between them (as in the AOL-TimeWarner case); and those between companies that were previously competitors, as in the constantly-growing brewery megacorp of Annheiser Busch. The latter is both much safer for investors, and much worse for customers, than the former; this type of merger has the direct goal of decreasing margin pressure by decreasing competition.