Ah, the omnipresent paradox of whether it is ever all right to tell lies, and the justifications that result from telling the "little white" ones. :)

I think my favorite thought on the matter comes from the aphoristic mouth of Thomas Szasz who wrote in The Myth of Mental Illness:

"Honesty is the best policy" is a familiar English saying. In Hungarian, an equally familiar saying is, "Tell the truth and get your head bashed in." The contradiction between these two proverbs is more apparent than real. In fact, each refers to a different social situation; and each is valid in its own context. Honesty is the best policy in instrumentally oriented relationships, and the worst in institutional settings. Einstein was rewarded for telling the truth in the open society of science; Galileo was punished for it in the closed society of the Church.

In other words, honesty is the best policy to adopt with those who are honest, and the worst to adopt with those who are dishonest. :)