Since we live in a hurry-up culture, it's not surprising that we like to find ways to speed up communication -- or at least appear to be doing so. But linguistic shortcuts are not an altogether new thing. Some have been around for centuries (at least), though one seems to me to be, if not exactly new, at least enjoying a current burst of popularity.
Speakers of English seem especially eager for ways to make their language faster, cleverer, sleeker. The English language may make our attempts more successful: we have always been unusually receptive to borrowings and neologisms, and our messy relationship between spelling and pronunciation may make English more forgiving of word-forms that don't adhere to conventional norms. Other languages do, of course, make use of neologisms, but English does so with especial élan.
We have several ways of doing this. One, perhaps the oldest, is truncation: simply snap off the end of a word. Thus mob, from Latin mobile vulgus, the "fickle crowd," going back to the 18th century. We regularly shorten long words in common use: microphone becomes "mike", vegetables morph into "veggies", and in England, television is "telly."
You can lop off the front end too: In the eighteenth century, omnibus (a vehicle for all -- Latin "omnibus") was promptly shortened to "bus". More recently we have formed "phone" (telephone), 'rents (parents) and 'fro (Afro), among others.
Starting somewhere in the middle of the twentieth century English speakers began to use acronyms -- in part as a way of getting some control over the bureaucracies and their bureaucratese that was beginning to create FDR's "alphabet soup." Acronyms are words formed from the initial letters of a phrase; they may form actual words of a language (NOW for National Organization for Women), or merely be pronounceable as if they were words (NATO, the North Atlantic Treaty Organization). A few acronyms survive from ancient times, chief among them ICHTHYS, standing for the Greek words for "Jesus Christ, son of God, Savior, " and spelling the Greek word for "fish."
People searching for etymologies for words that don't have them (often words with slang origins, since slang normally comes into a language orally and by the time a form shows up in writing, its sourcing is lost) often suggest an origin in acronyms, but this is almost never the case. Thus, you frequently hear that "tip" arose as TIP, "To Insure Promptness"; "posh" from "port out, starboard home," supposedly the best places for staterooms aboard ship. Neither of these is the likely origin of these words, but linguists don't know what is.
It is tempting to consider these acronyms as the sources of "tip" and "posh." But acronyms almost always start at the top: people in charge, government offices, and high-level discourse; slang, until very recently, always arose from below: the common people, criminals, pop entertainers, and teen-agers. So the idea that words that are first encountered in written representations of slang originated as acronyms is improbable.
Snappiest of our ways to make language snappier is the combination of two existing words into one. Lewis Carroll, in Through the Looking-Glass (1871) may have been the inventor of the genre, but was certainly the first to give it a name, the "portmanteau," or suitcase (because several different things could be packed in together). Humpty Dumpty, the semanticist, tells Alice that "slithy," in Jabberwocky, is such a form, derived from "lithe" and "slimy." (Linguistic scholars more recently have renamed forms like these "linguistic blends," proving to no one's surprise that Carroll was wittier than most of my colleagues.)
Of all these speedy options, the last seems the most currently productive and spontaneously generated. Over the last quarter-century, give or take, portmanteaus have extended their domain -- both in number and in type. Consider just a few that I have recently encountered (you probably can add to the list): frenemy, dramedy, infomercial, freemium (something you get for "free" if you are willing to pay for a service), Spanglish (and other similar coinages: Chinglish, Taglish (Tagalog), and, in French, franglais. More interesting perhaps is our current fad of combining the names of two celebrities who constitute a romantic item. The first such set I am aware of is Billary, Bill and Hillary Clinton, who were offered as a "twofer" president. That is perhaps an opening wedge for Brangelina, Bennifer, and their relatives. I also just recently encountered (on The View) tweeps, the people or peeps one tweets to, and twilter, a way to filter one's tweets. And in a commercial, colives, (referring to the composition of a spreadable product made from butter and olive oil).
It seems obvious that people create shortened forms to save time. And yet, most often, we don't save that much time and may run the risk of endangering intelligibility. So there must be other reasons why we find truncations, acronyms, and portmanteaus alluring. They are zingy -- they "pop." Using them suggests we are with it, cool, up-to-date, or that we are in the loop, members of the inner circle. They allow us to be creative with words, an area of language often considered fixed and inflexible.