  We address the question how string compactifications with D-branes are
consistent with the black hole bound, which arises in any theory with number of
particle species to which the black holes can evaporate. For the Kaluza-Klein
particles, both longitudinal and transversal to the D-branes, it is relatively
easy to see that the black hole bound is saturated, and the geometric relations
can be understood in the language of species-counting.
  We next address the question of the black hole evaporation into the higher
string states and discover, that contrary to the naive intuition, the
exponentially growing number of Regge states does not preclude the existence of
semi-classical black holes of sub-stringy size. Our analysis indicates that the
effective number of string resonances to which such micro black holes evaporate
is not exponentially large but is bounded by N = 1/g_s^2, which suggests the
interpretation of the well-known relation between the Planck and string scales
as the saturation of the black hole bound on the species number. In addition,
we also discuss some other issues in D-brane compactifications with a low
string scale of order TeV, such as the masses of light moduli fields.
