This is apparently not news to many educated folks; Isaac pointed me to an excellent essay by David Foster Wallace, "Tense Present," in which Wallace, who knew all about the inherent relativism of language standards but still had to teach English to actual young writers, strikes a delicate, well-modulated balance between the Descriptivists (who rightly point out that human languages are always and invariably evolving, to the consternation of self-appointed guardians) and the Prescriptivists (those self-appointed guardians). Wallace called for a more enlightened, self-aware, well-tempered prescriptivism--a stance in which agreed-upon rules of usage are not absolutes but merely guidelines toward the common goal of clarity and style in written communication. Wallace held up Bryan A. Garner's 1998 A Dictionary of Modern American Usage as a sneakily brilliant middle-of-the-road approach between the linguistic liberals and linguistic conservatives.
That said, can anyone tell me what's wrong with the following sentences?
Frankly, it's not fair.
Certainly, things are going to change.
Presumably, the change will be gradual.
Unfortunately, that's not fast enough for most of us.
Hopefully, it is going to change in our lifetimes.
The answer is so plunkingly obvious, I'm ashamed to say that I never thought of it (nor did anyone ever explain it to me.)