  In order to shed some light on the current discussion about f(R)-gravity
theories we derive and discuss the bounds imposed by the energy conditions on a
general f(R) functional form. The null and strong energy conditions in this
framework are derived from the Raychaudhuri's equation along with the
requirement that gravity is attractive, whereas the weak and dominant energy
conditions are stated from a comparison with the energy conditions that can be
obtained in a direct approach via an effective energy-momentum tensor for
f(R)-gravity. As a concrete application of the energy conditions to locally
homogeneous and isotropic f(R)-cosmology, the recent estimated values of the
deceleration and jerk parameters are used to examine the bounds from the weak
energy condition on the parameters of two families of f(R)-gravity theories.
