Prof. Geoff Nunberg (Language Log) has an excellent NPR “Fresh Air” item about the unfounded condemnation of “hopefully” as a sentence adverb. An excerpt:

That floating hopefully had been around for more than thirty years in respectable venues when a clutch of usage critics including Theodore Bernstein and E. B. White came down on it hard in the 1960’s. Writers who had been using it up to then said their mea culpas and pledged to forswear it. Its detractors were operatic in their vilifications. The poet Phyllis McGinley called it an abomination and said its adherents should be lynched, and the historian T. Harry Williams went so far as to pronounce it “the most horrible usage of our times” ….

You wouldn’t want to take the critics’ hysteria at face value. A usage can be really, really irritating, but that’s as far as it goes. You hear people saying that a misused “hopefully” or “literally” makes them want to put their shoe through the television screen, but nobody ever actually does that — what it really makes them want to do is tell you how they wanted to put a shoe through the television screen. It’s all for display, like rhesus monkeys baring their teeth and pounding the ground with their palms.

Of course even if you find the tone of these complaints histrionic, you can often sympathize with their substance. I feel a crepuscular wistfulness when I hear people confusing “enormity” with “enormousness” or “disinterested” with “uninterested.” It doesn’t herald the decline of the West, but it does signal another little unraveling of the threads of literary memory.

But the fixation with hopefully is different from those others…. [T]here’s no rational justification for condemning it. Some critics object that it’s a free-floating modifier (a Flying Dutchman adverb, James Kirkpatrick called it) that isn’t attached to the verb of the sentence but rather describes the speaker’s attitude. But floating modifiers are mother’s milk to English grammar — nobody objects to using “sadly,” “mercifully,” “thankfully” or “frankly” in exactly the same way.

Or people complain that “hopefully” doesn’t specifically indicate who’s doing the hoping. But neither does “it is to be hoped that,” which is the phrase that critics like Wilson Follett offer as a “natural” substitute. That’s what usage fetishism can drive you to — you cross out an adverb and replace it with a six-word impersonal passive construction and you tell yourself you’ve improved your writing.