  The current philosophy of impact hazard considers the danger from small
asteroids negligible. However, several facts claim for a revision of this
philosophy. In this paper, some of these facts are reviewed and discussed. It
is worth noting that while the impact frequency of Tunguska-like objects seems
to be higher than previously estimated, the atmospheric fragmentation is more
efficient than commonly thought. Indeed, data recorded from airbursts show that
small asteroids breakup at dynamical pressures lower than their mechanical
strength. This means that theoretical models are inconsistent with observations
and new models and data are required in order to understand the phenomena.
