  The recent Advanced LIGO detection of gravitational waves from the binary
black hole GW150914 suggests there exists a large population of merging binary
black holes in the Universe. Although most are too distant to be individually
resolved by advanced detectors, the superposition of gravitational waves from
many unresolvable binaries is expected to create an astrophysical stochastic
background. Recent results from the LIGO and Virgo collaborations show that
this astrophysical background is within reach of Advanced LIGO. In principle,
the binary black hole background encodes interesting astrophysical properties,
such as the mass distribution and redshift distribution of distant binaries.
However, we show that this information will be difficult to extract with the
current configuration of advanced detectors (and using current data analysis
tools). Additionally, the binary black hole background also constitutes a
foreground that limits the ability of advanced detectors to observe other
interesting stochastic background signals, for example from cosmic strings or
phase transitions in the early Universe. We quantify this effect.
