The dominant sources of energy production in the universe are fusion
in stars and gravitational accretion onto supermassive black holes.
The tight correlation between nuclear black hole mass and bulge mass
implies the processes are intimately connected. However, identifying
an unbiased census of black holes in the universe remains challenging,
hampering our ability to fully probe this connection. Furthermore,
the spectrum of the X-ray background, which is significantly harder than
that of bright, optically-selected quasars, requires a large population
of heavily-obscured AGN. Only a handful of luminous examples of this
population had been identified prior to recent years. Using data from
wide-area surveys with the Spitzer Space Telescope and the Chandra
X-Ray Observatory, we have recently uncovered a large population of
heavily obscured, luminous quasars. I discuss the properties of this
population, the relative merits of selection at different wavelengths,
and how this population relates to unified models of active galaxies.
I will also highlight other exciting science enabled by these wide-area,
multi-wavelength surveys, and conclude with future prospects with warm
Spitzer surveys and upcoming NASA missions such as WISE and NuSTAR.