[aamar]

Okay. I think those sources are descriptive, but to be sure, here is the American Heritage Dictionary (http://dictionary.reference.com/browse/irony), an explicitly descriptive dictionary about American usage. It seems to agree with the other sources that irony can be and is often used in this case.

On the other hand, one can reasonably believe that every dictionary is, by its nature as a reference book, primarily prescriptive (and proscriptive) and therefore cannot be reliably descriptive. If so, then it seems we do have to go only with personal observations.

In terms of personal observations, I agree with you that many Americans I know would use "sarcasm" in this case and not use "irony." I think I (along with many other Americans, maybe fewer than the other group?) would use "irony" and probably not use "sarcasm" because it doesn't have that particular, hard-to-miss sarcastic tone of voice.