Good question. I am currently 0/6 in onsites, and 7/7 in technical phone screens. I anticipate having more interviews in the next couple of weeks, as I have no shortage of opportunities in my inbox.
I would start taking detailed notes of the types of questions that you are being asked in person and examine the initial reactions of the people that are performing the interviews. There's something hidden somewhere in the interview and you can find it if you read the situation carefully.
Last note quick => I would REALLY REALLY dig in and make sure these are even companies that you would want to work for... just because they want to hire you doesn't mean that its a good fit for you. And despite what it may seem (the way companies run around pretending that you should feel fortunate to work for them) the consequences of taking a job that is a bad fit are significantly worse to you than for them to make a bad hire.