A "vaad" is a council of rabbis, like the RCC, the dominant Jewish law court in California.
Marc B. Shapiro blogs: Experience has shown that a rabbi who is financially corrupt can easily win back his reputation (and in some circles financial corruption doesn’t affect his reputation to begin with). Yet if a rabbi is accused of not being reliable in matters of kashrut, even if the accusation is false, it is almost impossible for him to turn this around. Unfortunately, when it comes to kashrut supervision, American Orthodoxy has distorted our tradition. People are constantly told that if they see a hashgachah on a product or restaurant, that they cannot rely on it without investigating who the rav ha-machshir is. This is completely mistaken. According to halakhah every rav is regarded as trustworthy unless you have been reliably informed otherwise. Without receiving negative information, one should always assume that a rav is reliable. This is no different than if you arrive in a new city and go to shul on Shabbat and you are invited to someone’s house for lunch. One should assume, unless he has reason to think otherwise, that the person inviting him keeps kosher, as religious Jews have a hezkat kashrut. Certainly, if the rabbi invites you to his house you must assume this. The notion that is currently rampant, that we don’t trust a rav until we investigate him, is the exact opposite of what the tradition has always held. Rather, we are supposed to trust the rav unless we are given reason to think otherwise. Every rav, even a rav ha-machshir, has a hezkat kashrut and is assumed to be doing his job reliably.
To show how far this idiocy has gone, let me share something that happened a couple of years ago when I was visiting a city that shall remain nameless. Someone was eating with us and mentioned that he was going to be travelling to Elizabeth, New Jersey. He asked me if I knew about kosher food in the area. I told him that Elizabeth has a very nice Jewish community, with plenty of kosher food. He then asked who gave the hashgachah, and I replied that it is Rabbi Teitz. The man wasn’t happy with my answer, which troubled me since I had never heard of anyone question R. Teitz. In fact, in speaking to him it was apparent that he had never even heard of R. Teitz. Yet he announced for everyone that his family would have to avoid visiting any of the kosher eateries when he was in Elizabeth. I was really shocked and I asked him, "Why? What is wrong with R. Teitz?" I further asked him where he thinks the people he will be visiting in Elizabeth get their food. Yet he would only reply: "We only eat at places under the supervision of a Vaad." I told him that I didn’t think that there was a Vaad in Elizabeth, and why in any case does he need a Vaad? A Vaad might be a good idea from a practical standpoint, in order to create one communal standard, yet there is nothing in the Shulhan Arukh about a Vaad, and R. Teitz is as reliable as anyone. Yet all I got from him was the same nonsense about how without a Vaad a hashgachah cannot be trusted. (I never asked him what he would do in a one-rabbi town.)