Raymond Chen, noble defender of language, pointed out today that fellow Microsofties have now taken to inventing adjectives, in addition to nouns and verbs. Though Raymond's example is pretty benign, it does bring out the usual champions for language purity and for language malleability to re-enact the age-old argument.
I don't really consider myself a language purist. I have been known to twist words until they cry uncle, and create connotations and juxtapositions that will leave you groaning. (Ask my co-workers sometime about their reaction when I would casually mention in scrum how a bug was caused by another module molesting my class variables). You also don't see me running around spouting "thou" and "wherefore" when I mean "you" and "why" (though you don't see language purists spouting that either, which gives lie to a straw-man argument). In this case, though, I'm going to have to go with Raymond's side.
Language is meant for communication. Communication is only fostered when both the sender and the recipient can rely on a common vocabulary to make certain that meaning is preserved. When you make up a word, the common vocabulary is broken, meaning is lost, and communication doesn't work. Even with words like "planful", where a smart recipient can usually puzzle it out, there is still a break in conversation as the recipient puzzles it out, and they still might get it wrong (Is it something which has too much plan? Perhaps a clever play on 'painful'?)
Yes, it is true that language evolves. But just as with biological evolution, it changes over the course of generations, and not individuals. Language evolves primarily in two ways. New words are created for concepts that had none, and new people learn the language with a slightly different vocabulary from their predecessors. If you use a new buzzword because last week's word for the same thing doesn't have the right punch, then you're not evolving language. You're making stuff up, and muddling your message because of it.
To quote Humpty Dumpty (Lewis Carroll -- "Through the Looking Glass"):
When I use a word,' Humpty Dumpty said, in rather a scornful tone, `it means just what I choose it to mean -- neither more nor less.'
However, to paraphrase what a much wiser orator once said to me in response to the above line:
That's total bull. When I hear the word, it means what I think it means, because I'm the one being spoken to, and you're the one spouting nonsense.
I couldn't have phrased it better.