This will actually be far too brief to make a blog post around, but alas...
What is "overrated"? Many things, apparently, but so far as I can tell the word itself is used to describe something that too many people like, or that is well liked for little reason.
This is an inherently subjective word. Infuriatingly so. At its most basic, it means "too many people have a different opinion than mine", which if phrased that way means nothing. Yet so many people employ the word. There is no such thing as "other people like X too much". It is precisely because people have different opinions that some thing's are successes and others are not, and if something is a success, then it is, for that very reason, not overrated -- if people like something, that something must've done something to deserve it, whether you understand what that is or not, because thousands of people don't like something "just because". And I suppose that's just where the issue lies. Once again, people have different opinions. It's that simple.
Such a shame it doesn't stop me from hating the word. It has no purpose. It's obvious and always implied whenever anyone has an opinion, and it only serves to bring a bad connotation and disagree with other peoples' opinions. "Underrated" at least has a purpose (in this context. Other contexts, more similar to "underestimate" are a different, unrelated, story); not to say people don't "like something enough" or people "dislike something too much", which is also another way to spell "too many people have a different opinion from mine", but to say that not enough people know of a particular thing. "Not enough people know about X", or "Not enough people gave X a chance".
You can use "overrated" properly. "The importance of X is overrated" can be used to describe situations where misinformation is popularly spread. But therein lies the key. Using it in "subjective" matters, in matters of opinion, means little. It's a way of complaining that other people have different opinions. And I dislike that, so I complain about it on forums online.
This post was sponsored by that thread asking if CLANNAD deserves its popularity or if it's overrated. I'd say when something makes you ask if it is "overrated", that's because it is popular to a point where it must have done some things the proletariat likes, and therefore can't be overrated.
Of course, that doesn't remove the merit of discussing what is "well done" or "badly done" according to other people.