During interview (Unfortunately, we can hardly to check all items in an interview session) we can able to appraise which overstated competence is ignorance which one is lie

While I can see where you come from when saying that, it is almost always the case that when a candidate adds a buzz word into his CV (i.e. Ajax), he must have possessed a certain piece of knowledge about it. That guy may happen to never ever written any Ajax application, and only have read about it in one or two articles. He may feel insecured about his knowledge about Ajax and he may be aware that he does not know enough about the thing to be productive with it. But damn it, he thinks he knows it and he should be able to include it in his CV. So, with this candidate, can you say he is a liar, an ignorant person (or an ignorant liar)?

On the other hand, it’s true that there is a number of candidates who may intentionally cheat by listing Ruby in their CV just because they know it is a programming language (without even know about any syntax). But I would suppose this number is really small (otherwise, that guy must be really really “courageous” and, in addition, it is very unfortunate for the software industry).

And yes, as you said, we can hardly assess all the things the guy says (or lies) in his CVs, the focus should be on the assessment of things necessary for the him to get the job done in his applied position. If he applied for a Java developer position, assess whatever necessary knowledge for that position, otherwise, you would spend all of your productive interviewing time to detect lies, which does not worth the effort for the reasons I mention above.