Lattice QCD calculations of B meson properties and consequences for quark flavor phenomenology

Lattice QCD calculations now include the effects of 2 light sea quarks and 1 strange sea quark through the use of an improved staggered fermion action. Consequently, results important to phenomenology are free of the approximate 10\% errors inherent in the quenched approximation. This talk reports on calculations of the $B$ and $B_s$ decay constants, matrix elements relevant for neutral $B$ meson mixing, and $B \to \pi \ell \nu$ form factors. The focus of the talk will be on the current lattice uncertainties, the prospects for reducing them, and the role the results will play in flavor physics phenomenology.