  Recent studies of dense clumps/cores in a number of regions of low-mass star
formation have shown that the mass distribution of these clumps closely
resembles the initial mass function (IMF) of field stars. One possible
interpretation of these observations is that we are witnessing the
fragmentation of the clouds into the IMF, and the observed clumps are bound
pre-stellar cores. In this paper, we highlight a potential difficulty in this
interpretation, namely that clumps of varying mass are likely to have
systematically varying lifetimes. This timescale problem can effectively
destroy the similarity bewteen the clump and stellar mass functions, such that
a stellar-like clump mass function (CMF) results in a much steeper stellar IMF.
We also discuss some ways in which this problem may be avoided.
