No, not all; however there are several pseudoscientists listed amongst those who've done outstanding work. Neither appeal to authority nor quote-mining provides empirical evidence demonstrating the existence of extraterrestrials nor their often-claimed presence here on Earth. Do remember that the possession of a PhD does not automatically guarantee the validity of one's claims and/or research -- and more importantly, that the plural of anecdote is not data.

As an example, I had the opportunity to hear Dr. Leo Sprinkle and his claims on an Internet-based "radio" program back in the fall of 2003. His methodology is ultimately flawed and conclusions wholly unsupported empirically. Here is a verbatim transcript of my interaction with Sprinkle (and if anyone's interested, I do have the audio file for this but not enough room to host it):

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Me: Dr. Sprinkle, earlier in the program when you were describing how some of your viewpoints weren't very well recieved by others in academic circles, in response to the criticisms, you introduced the question "Is this the way science is supposed to work?"
Sound scientific methodology, as I'm sure you're aware, attempts to minimize the influence of bias or prejudice in the experimenter when testing a theory or hypothesis. Since, over the course of tonight's program, you've openly described personal biases and speculations in your approach to this research, how can your work ultimately yield empirical data when it seemingly disregards crucial elements of the scientific method of inquiry?

Sprinkle: Thank you very much for your question.

(program host) Jim Hickman: Wow...[laughs]

Sprinkle: In my opinion, uh, you are using an outdated, uh, model of science. It used to be thought that the experimenter should be separate from the experiment. Nowadays, the physicists, uh, are saying that, uh, the observer, uh, influences the uh, the behavior of the photon... uh, whether it's particle or wave is partly based upon the consciousness of the physicist. And so most, uh, psychologists tend to follow biologists, most biologists tend to follow, uh, physicists, and so, uh, I'm claiming [clears throat], and if you are interested, uh, there's a man named Rosenthal, Robert Rosenthal, he's now at Riverside, uh, University of California, Riverside, he used to be at Harvard, and I knew him when he was at the University of North Dakota back in the 60s. He's written many books, uh, including one called, uh Exp... the uh... let's see ... it's about experimenter bias, and it's about uh, I think it's called Exper... Experimenter and... uh the Laboratory, the Laboratory and the Experiment, something like that, Appleton/Croft/Century 1966 book. And uh, [clears throat] and he found that EVERY OBSERVER, EVERY EXPERIMENTER IS BIASED. LISTEN TO ME SIR, EVERY EXPERIMENTER IS BIASED. And the best way to deal with it is to be AWARE of one's bias. If one is aware of one's bias then one can help safeguard against... uh, finding, uh, data that are inappropriate or that are a distortion of, what, uh is going on. But I'm trying to be aware of my bias, [clears throat], and I'm claiming that your bias is, uh, that you believe the experimenter is separate from the experiment, and in my opinion, the experimenter cannot be separate because ESP studies show there is still a connection. So if we are aware of our bias, then we can help ourselves by looking through our lens, just like I have glasses, and uh, they... they're not my natural eyesight but my natural eyesight is not as good as if I have my spectacles, so if I know that my bias is, I can look at things through that bias and see if that's the way other people are looking at it. And uh...

Hickman: My question to...

Sprinkle: Yeah, go ahead...

Hickman: ... to scientists is "how can we apply the scientific method to UFOs that pop in and out of the sky?"

Sprinkle: [Laughs] That's a beautiful question, and the only way we can do it, in my opinion, is to get acquainted with who's popping in and out of the skies.

Hickman: [Laughs]

Sprinkle: [Laughs]
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[-X Sprinkle is no more a scientist than I'm an astronaut.

IMHO, the probability for the existence of some variety of extraterrestrial life in the universe is significant, given our present understanding of its vast expanse. That being said though, mere belief in same does not satisfy the criteria required to demonstrate such. Skepticism is definitely warranted where extraordinary claims are concerned, regardless of one's personal desire to embrace them as true.