It seems that the U.S. Postal Service has managed to mess up the whole Maya Angelou stamp issuance thing before it even happens.
According to the Washington Post, the quote attributed to Angelou on the stamp is not even hers:
In the Postal Service's defense, they are not the first to make this particular mistake. Over the years, that quote has become linked in the minds of lots of people to Angelou's autobiography, I Know Why the Caged Bird Sings.“A bird doesn’t sing because it has an answer, it sings because it has a song,” the Angelou “Forever” stamp reads.“Yes, that’s my quote,” (Joan Walsh) Anglund said Monday night from her Connecticut home. It appears on page 15 of her book of poems “A Cup of Sun,” published in 1967. Only the pronouns and punctuation are changed, from “he” in Anglund’s original to “it” on the stamp.