The English language is not sick. It is not even afflicted with a head cold, much less languishing on its deathbed. Nor is it under attack: there are no nefarious forces conspiring to change it from an eloquent tongue to a series of grunt and emoticons. The attitude of some of its speakers, however, seems to be that the barbarians are not just at the gate, they have already stormed them and are destroying the foundations of a once-mighty language.
We often hear people furiously insisting that decimate should only be used to refer to the punishing or killing of one of every ten people, or that friend is not a verb, no matter what Facebook says. These sentiments overlook the fact that before decimate referred to a military punishment it was used to refer to the act of tithing (a sense that no one seems eager to resurrect), and friend has been used as a verb in English for about 800 years.
While I applaud having a passion for language, I cannot condone the way that many choose to express this passion, which is by telling other people that they are wrong in how they use their words.
Words change their meanings. You may not like this, but your dislike of the broadened sense of literally will not cause it to cease to exist. If you want proof that words can change meanings without causing civilization to spontaneously implode all you have to do is look at some of the words that were annoying people not so long ago, and which we all use today. Here is a sample of some of the words that were causing unrest in the 19th and early 20th centuries:
Mansion - If you are in the habit of referring to an ostentatiously large residence as a mansion you would have run afoul of Emily Post. The doyenne of American etiquette felt that this was a word that should never be used (she recommended saying 'large house'). In addition to this, Post suggested that people also avoid using the word drapes, mortician, and photo (as opposed to the more refined words curtains, funeral director, and photograph).
Ovation - Ambrose Bierce, the gloriously splenetic author of The Devil's Dictionary (1909), also wrote a usage guide for the English language, titled Write it Right. Bierce strongly felt that ovation should not be used to refer to considerable applause, since it came from a similar Latin word that described the reception given to a military commander who had a minor triumph.
Gender - Henry Fowler, the celebrated author of A Dictionary of Modern English Usage (1926), insisted (despite considerable evidence to the contrary) that gender was "a grammatical term only." Fowler felt that people using this word to refer to a person's sex were either being intentionally jocular or were simply wrong.
Awful - If you've ever noticed the incongruity in how many people like to complain about teenagers using the word awesome to refer to things that do not actually cause awe, yet themselves use awful to describe things that are not actually full of awe, you are not alone. Josephine Baker (the language writer, not the dancer) noticed this as well, and in her 1899 book The Correct Word insisted that "awful means inspiring with awe."
Jeopardize - Many people like to wax dyspeptic about words that end in -ize, and we often hear complaints about such specimens as incentivize and hospitalize. We may add jeopardize to the list of -ize words that have raised hackles, as Richard Grant White, in his 1882 book Words and Their Uses stated that it was "a foolish and intolerable word, which has no rightful place in the language."
Talented - It may not be immediately apparent to many of you what the problem is with the word talented, but it cause great anguish to the poet Samuel Taylor Coleridge, who referred to it as "vile and barbarous" in Specimens of the Table Talk, an 1835 collection of his writing. Coleridge's objection was based on the notion that the word was formed from talent, which to him was properly used only as a monetary measurement, and he sarcastically suggested that if talented was accepted, shillinged and tenpenced should be considered as well.
These are but a handful of thousands of words that we all freely use today, but which have been viewed as sub-literate or vulgar at some previous point. If these once-censured words can assimilate into the accepted vocabulary of English then there is no reason that OMG, irregardless, and other frowned-upon words cannot follow the same path at some point in the future.
Calm down. The English language is a fine and healthy specimen, squalling and growing, and it is behaving exactly as a living language should, which is to say that it is changing. If you find yourself so uncomfortable with this that you cannot resist the urge to tell people that the word they just used 'is not a word', or if you constantly feel the need to inform others that the words they used mean something other than they thought, well, that is really more your problem than theirs.
No matter how much you insist on trying to preserve the meanings of certain words, you will be unable to stem the tide of semantic drift that English (and all other living languages) are prone to. That's the bad news. The good news is that there are plenty of languages in which words do not change meaning, and so if you'd like an unchanging language you have many to choose from. The vocabularies of Latin, Coptic, Magadhi Prakrit, and hundreds of other extinct languages tend to change very little. Granted, it may be difficult to learn these languages, but I can guarantee that it will be easier than trying to 'fix' the way the rest of us use English, and will be considerably less annoying.