Doing it once can be chalked up to simple ignorance -- a readily treatable condition.
In part, it a matter of respect -- of taking it seriously. People who refuse to respect the convention convey the message that they don't care or worse. People who get all exercised about being called on it elevate themselves to the category of stupid -- an untreatable condition.
I note that the author of the original post didn't get exercised about being called on this point. Clearly, he is genuinely trying to take in such hints and clues as are being proffered here to make his recruiting problem lesser.
As an aside: I don't know if Sun has defined exactly how java *should* be capitalized. I do know that Larry has done exactly that for Perl.