> Maybe the (alleged) second meaning isn't the MOST common usage, but it is quite common, whether this is regrettable or not. I think that the meaning's popularity grants it legitimacy. I suggest that if one person misuses a word, that person is wrong, but if (big number: say 50 million) people misuse it, the dictionaries are wrong.

I would go the other way and say dictionaries aren't even as strict as they *should* be, as evidenced by the reprehensible Merriam-Webster adopting, for the second cited time in this message forum, an incorrect common use definition.
But that's neither here nor there, so I'll address your point.

Language does indeed evolve, and perhaps the seeds of some pieces of that evolution have their origins in misunderstandings. However, no matter how many people use "peruse" to mean "skim" today, I won't accept it until a significant number of actual educated linguists and scholars of the English language adopt it also. I realize this is bound to be an unpopular opinion, just for the image linguist perfectionists have, and the natural suspicion people have toward experts in non-exact fields (like science), either from a perceived pompousness or out of a subconscious jealousy. But irrational feelings as these aside, it makes perfect sense. If a change to language with seeds in a common error are to take place, even the experts, in due time, will be forced to acknowledge it.

But in today's society, where such an unfortunate number of people are illiterate or close to it, it would be utterly chaotic if English evolved as quickly as people thought up new incorrect uses for it. "Peruse" is the perfect example. If we accept "skim" as one of its definitions, we have just utterly destroyed the word. Destroyed it. It's of absolutely no value whatsoever if it's permitted to be its own antonym. Alas, there are a number of other words also well on their way to extinction -- good, fine, previously succinct words that just won't be useful anymore. Was it Mark Twain that said that for every situation, there is exactly one right word and dozens of wrong ones? I don't think I hold such an absolute position myself, but it is certainly true that there are *many* situations in which there's really only one right word -- by destroying words through ignorance, we limit English's breadth and power.

And there is another very good reason for listening to the English-language scholars, rather than street usage, to channel the evolution of our language (besides that adhering to street usage technically isn't evolution at all but devolution), and that is that in most of the places that really count, you'll get nailed if you use language in a dubious way. Any editor worth his salt will choke on a use of "peruse" to mean "scan" (or "enormity" to mean "enormousness") and other such misuses, and your value as a writer will be swiftly diminished in the eyes of people that hold careers in their hands for a living -- and this is just an example of where careless word use can get you into real trouble.

So in conclusion I understand that language evolves, but deny that this is in itself justification that we should let it evolve in whatever random direction there seems to be a remotely prevalent tendency for it to lean in. Nothing good has ever come from letting language evolve through ignorance. (Just look at "flammable" vs "inflammable": "inflammable" was once misunderstood to mean its opposite, and now it's common AND accepted for "inflammable" to mean "flammable." Is there anyone here that can question that this was a bad idea and should have been fought back when the misuse was first occurring?)