  21 cm tomography is emerging as a promising probe of the cosmological dark
ages and the epoch of reionization, as well as a tool for observational
cosmology in general. However, serious sources of foreground contamination must
be subtracted for experimental efforts to be viable. In this paper, we focus on
the removal of unresolved extragalactic point sources with smooth spectra, and
evaluate how the residual foreground contamination after cleaning depends on
instrumental and algorithmic parameters. A crucial but often ignored
complication is that the synthesized beam of an interferometer array shrinks
towards higher frequency, causing complicated frequency structure in each sky
pixel as "frizz" far from the beam center contracts across unresolved radio
sources. We find that current-generation experiments should nonetheless be able
to clean out this points source contamination adequately, and quantify the
instrumental and algorithmic design specifications required to meet this
foreground challenge.
