Is not wearing a NECKTIE less formal or less professional?

I think it depends what kind of company we are talking about. I think, if we talk about any high-profile, really serious companies, it's less professional and downright rude not to wear a tie. But if we talk about a really modern, casual multinational company or a laid-back company where creativity is the most important thing, I don't think it's that much of a mistake. But as for a job interview, I would wear a tie, just in case. Just something not too old-looking or out of style. After that, the person is probably going to be introduced to a dress code or see how the coworkers dress.

Well it depands from the job. If you go for some serious interview or meeting then you have to wear a nectie. I think in a job interview you wear the clothes in wich you going to work. Thats way you show your profesionalism.

No, i do not think that when you show up at work, or for an interview in a company not wearing a tie meant you are not professional. Many are not offended by this, unless it was strictly stated to go formal during the interview. I have been to many interviews, and have seen a lot of interviewees in the previous companies i have worked with and it was not a point less in the person's chance of being hired (one is hired because of his skills and experience. i think the only one that would rather blow off his application is when he shows up not in an attire suitable for a professional working in an office environment(say, a t-shirt, baggy pants, or even shorts! haha)

No necktie is just less formal. You are still a professional without necktie. If you go to the gathering you should ask what is the attire to be wear, if its formal or semi-formal attire.