The T-shirt in the comic above actually exists. So we’ve arrived at a situation where people don’t even proofread clothing.
Actually, I remember a friend who works in the printing business telling me a while back that it’s not the responsibility of the printing company to proofread or correct things like this; it’s the original designer’s fault. And it’s true—it is the original designer’s fault and they should be ridiculed for producing it (especially as it’s a pretty shitty design anyway), not to mention the idiots who pay money for it. I know for a fact if I was asked to print the T-shirt above I’d find it incredibly difficult to not correct it, though.
The reason? I believe in the sanctity of language. That’s a pretentious way of saying that I believe strongly that we should continue to spell things “correctly”. I know, I know, language changes over time and all that. But the reason we have certain rules in place with today’s modern form of English is to aid understanding.
Take “your” vs. “you’re”. We have two forms of “your/you’re” to prevent ambiguity. “You’re”, as everyone knows* is short for “you are”, with the apostrophe denoting that at least one letter has been removed to form a contraction. “Your”, on the other hand, is simply a possessive pronoun used as a an attributive adjective showing when something belongs to “you”. “If your single, so am I” doesn’t make any grammatical sense because, assuming that “single” is being used as a noun (which it should be if it’s following the word “your”) it needs a verb, otherwise the response to the T-shirt’s slogan is “If my single is what?”. “If you’re single, so am I” does make sense, however, because it’s saying “If you are single, so am I”. Which is a stupid and somewhat sluttish statement to make, but grammatically correct.
Unless, of course, they were going for a very heavily-buried programming joke. You know, like when you’re programming in C or something similar and instead of saying “if (single = true) { haveSexWithMe(); };” you can instead say “if (single) { haveSexWithMe(); };”. Essentially, then, suggesting that the full slogan is in fact “If your single status is firmly confirmed without any possibility of you being a cheating skank-basket, you can assume I am also single, even if I am not in reality”, but shortened to fit across someone’s boobies. I somehow think this scenario is unlikely, however.
Some accuse people who get riled about this sort of thing of being snobs. And perhaps we are; but to my mind, there’s not really a good excuse for using the wrong “your”. It’s two extra keystrokes to type “you’re”, a couple more flicks of the pen. We’re taught how to use “your” and “you’re” in primary school. I know plenty of people who have difficulties such as dyslexia who still know how to use the correct form of “your” and do so.
The only explanation I can come up with, then, is either laziness, ignorance or both. In an environment such as the Internet, your (yes, YOUR) written words are how you make your first impression. In reality you don’t walk into crowded rooms shouting “HERP DERP HERP”, belming and masturbating furiously, do you? So make sure you use the right word once in a while, hmm?**
I'm Not Doctor Who 