  There is an ongoing debate in the literature as to whether the effects of
averaging out inhomogeneities (``backreaction'') in Cosmology can be large
enough to account for the acceleration of the scale factor in the FLRW models.
In particular, some simple models of structure formation studied in the
literature seem to indicate that this is indeed possible, and it has also been
suggested that the perturbed FLRW framework is no longer a good approximation
during structure formation, when the density contrast becomes nonlinear. In
this work we attempt to clarify the situation to some extent, using a fully
relativistic model of pressureless spherical collapse. We find that whereas
averaging during structure formation can lead to acceleration via a selective
choice of averaging domains, the acceleration is not present when more generic
domains are used for averaging. Further, we show that for most of the duration
of the collapse, matter velocities remain small, and the perturbed FLRW form of
the metric can be explicitly recovered, in the structure formation phase. We
also discuss the fact that the magnitude of the average effects of
inhomogeneities depends on the scale of averaging, and while it may not be
completely negligible on intermediate scales, it is expected to remain small
when averaging on suitably large scales.
