One of the things I hear most often from business owners who engage my freelance copywriting services is, "I never do my own writing because I just know I'll get the spelling and grammar all wring." Well, of course effective copywriting requires a lot more than just a firm grasp of spelling and grammar. In fact, some of the most powerful marketing content deliberately plays fast and loose with those rules. Let's take a look at those instances in which breaking the rules can be good.
We've all seen examples of riotously incorrect ad slogans over the years. Half a century ago, Winston offered up the famous declaration "Winston tastes good like a cigarette should," sparking immediate controversy over its misuse of "like" as a conjunction. Would it have been more correct to say "Winston tastes good as a cigarette should?" Certainly. But would the slogan have been swept into the public consciousness to anywhere near the same degree? No way!
(The tobacco industry seems to have had ongoing issues with grammar. "Us Tarrytown smokers would rather fight than switch!" was another faux pas that nevertheless caught on with the public. Perhaps a new medical study is in order....)
Geeks worldwide know and love (or hate) Apple's encouragement to "Think Different." I was just beginning my writing career when that campaign first launched, and I remember some English majors sneering about how Apple's proofreader was asleep on the job. Surely the company meant "Think Differently!" But they missed the point entirely: Apple was using "different" as a concept -- a way of life, not a modifier.
My various writing instructors used to insist that you have to know the rules before you can break them. In other words, if you understand a rule and then break it intentionally, you're creating a deliberate effect and not an ordinary screw-up. If you're quoting a certain famous cartoon bird, for instance, you can't correct his speech to read "I thought I saw a pussycat," because you'll lose the whole pop-cultural context and you won't be making your point (whatever that is).
So, yes, you can break the rules. You may even want to. But let us know, somehow, that you know what you're doing and why you're doing it -- and make sure the result is genuinely compelling. Heed the wise words of the members of Spinal Tap: "It's such a fine line between stupid and clever."