I have many friends who had told me that I can be turned back at the US airport even with a valid passport and visa. I am coming on visit and I want to be able to go back and forth, I don't want to live here but i have a lot of dear friends and I want to come back on vacations, they keep telling me I won't because they stop you at the airport even when you have a valid passport and visa.
Is that true? can they do that at will? if the agent doesn't like you, can he be turned back?

I do not know of any in my friends and family circle who have been sent back at the airport with a valid visa including a tourist visa. Many of them have been coming and going like you say on a visitor visa for years. I find it hard to believe that you could be sent back or denied entry unless there is a fraud or criminal activity involved.
sk

JDS, the fact that you have a valid visitor visa does not mean that you are guaranteed entry to the USA. The point is that you must proof to the immigration officer upon arrival at the airport or wherever you enter that you do not intend to stay in the US. You must have proof of your ties to your home country like a job waiting, a house, mortgage payments, wife, kids, whatever. You must also have enough cash to support yourself and you need an address for where you are staying. Just proof that you do NOT intend to stay in the USA and that you can support yourself, and you should not have a problem to get the visa in your country nor getting entry to the USA. HAVE FUN!