Etre un homme utile m'a paru toujours quelque chose de bien hideux. To be useful has always seemed to me quite hideous.

-Baudelaire, Charles
  Mon coeur mis a'   nu, pt.9.

Heureux, qui comme Ulysse, a fait un beau voyage, Ou comme cestuy la'   qui conquit la toison, Et puis est retourne¤  , plein d'usage et raison, Vivre entre ses parents le reste de son a"  ge! Happy is he who, like Ulysses, has taken a wondrous journey Or has won the Golden Fleece, And then returns home wise and useful To live in his homeland the rest of his days.

-Bellay,Joachim du
  Les Regrets, no.31.

A science is said to be useful if its development tends to accentuate the existing inequities in the distribution of wealth, or more directly promotes the destruction of human life.

-Hardy, Godfrey Harold
A Mathematician's  Apology.

[There is] a delusion that macro-economics is both viableanduseful (a delusionencouraged by its extensive use of mathematics, which must always impress politicians lacking any mathematical education, and which is really the nearest thing to the practice of magic that occurs among professional economists).

-Hayek, Friedrich August von
  The Fatal Conceit:  The Errors of Socialism, ch.6.

Ex virtute absoluto agere nihil aliud in nobis est, quam ex ductu Rationis agere, vivere, suum esse conservare (haec tria idem significant) ex fundamento proprium utile quaerendi. To act absolutely according to virtue is nothing else in us than to act under the guidance of reason, to live so, and to preserve one's being (these three have the same meaning) onthebasis of seeking what isusefulto oneself.

-Spinoza, Baruch also known as Benedict de Spinoza
  Ethics, bk.4, prop.24.