  The faint radio point sources that are unresolved in cosmic microwave
background (CMB) anisotropy maps are likely to be a biased tracer of the
large-scale structure dark matter distribution. While the shot-noise
contribution to the angular power spectrum of unresolved radio point sources is
included either when optimally constructing the CMB angular power spectrum, as
with WMAP data, or when extracting cosmological parameters, we suggest that
clustering part of the point source power spectrum should also be included.
This is especially necessary at high frequencies above 150 GHz, where the
clustering of far-IR sources is expected to dominate the shot-noise level of
the angular power spectrum at tens of arcminute angular scales of both radio
and sub-mm sources. We make an estimate of source clustering of unresolved
radio sources in both WMAP and ACBAR, and marginalize over the amplitude of
source clustering in each CMB data set when model fitting for cosmological
parameters. For the combination of WMAP 5-year data and ACBAR, we find that the
spectral index changes from the value of $0.963 \pm 0.014$ to $0.959 \pm 0.014$
(at 68% c.l.) when the clustering power spectrum of point sources is included
in model fits. While we find that the differences are marginal with and without
source clustering in current data, it may be necessary to account for source
clustering with future datasets such as Planck, especially to properly model
fit anisotropies at arcminute angular scales. If clustering is not accounted
and point sources are modeled with a shot-noise only out to $l \sim 2000$, the
spectral index will be biased by about 1.5$\sigma$.
