Only if you plan on sticking wings on the thing. The simple explanation (that will make actual aerodynamicists cry) is that the wings suddenly increase the frontal area a lot at the particular cross-section of the fuselage where they're mounted, so you have to subtract some of it from somewhere else. Aaaaand I just noticed that several people already pointed this out. Darn my attention span. On a related note, notice how the back ends of some of those teardrop designs taper more sharply at first before flowing into a longer, thinner tail? I *think* this is because the air getting squeezed past the body is going to "snap back" more quickly just past the widest point, and then slower and slower as the pressure lessens.