The advent of the digital revolution is only the latest phase in the eclipse of the oral tradition in language use by practices derived from the sphere of the written word. Thus when a radio announcer mispronounces chicanery by rendering the stressed vowel so as to rhyme with can rather than cane, he is clearly relying on a habit of reading, not speaking, which produces American English [æ] instead of (British English) Anglicized [ā]. One can safely guess that he has never actually heard the word pronounced by a speaker who knows the correct form.
Never hearing some words of English lexis is clearly becoming the common experience of a growing number of speakers of American English. This is evidently what accounts for the establishment of incorrect stresses like cónsummate (the adjective, not the verb) among even educated speakers for what in the English oral tradition is consúmmate [kənˈsʌmət] (cf. the differential designations for the corresponding entry in the Cambridge English Pronouncing Dictionary, 16th ed.).
On an autobiographical note, it was in fact only when I first heard the word pronounced correctly from a paragon of English diction, my late wife Marianne (of blessed memory) that I changed my own prosodic habits to comport with those of someone who had evidently imbibed it herself from her early orthoepic models and, more importantly, embodied its meaning in her own person. Мир праху ее.
[Addendum, 2/27/12: On the BBC World Service today, one could hear a clip from an interview with Eileen Chamberlain Donahoe, U.S. Ambassador to the Human Rights Council, who mispronounced the word patently ‘obviously’ in the phrase “patently ridiculous,” which even in standard American English has a traditional stressed vowel in this meaning that conforms to the British (rhymes with latent) rather than the American norm for the word patent.]