We haven't even scratched the surface towards a comprehensive search. Which frequency, where, what sensitivity, what polarization, etc. My search is looking strait down our spiral arm. The most bang for the buck per say. But even when I finish my upgrade, I will still be only scanning 30 million frequencies. A tiny drop in the bucket.
There is also the problem of efficiently transmitted signals being essentially indistinguishable from noise. It took human civilization an extraordinarily short amount of time from the first usable radio transmissions to extremely efficient transmission coding (which is just starting to become common here). It is improbable that SETI will trip over that narrow window, when the practical civilization window is millions and billions of years. It doesn't help to be able to receive a signal if you can't tell that it IS signal.
I wonder if this is a legitimate way to look at things: Imagine a caveman who knows absolutely nothing about mathematics or mathematical logic; i.e., he is totally incapable of rigorous deductive and/or inductive reasoning (therefore, any conclusions he reaches are based only on his eyeballing of the data, and not on his ability to derive any logical consequences).
Now, I believe if you gave this caveman a sample of several hundred positive integers selected randomly from the first, say, 1015 positive integers (far more than the number of stars in the galaxy), and he were willing to stick out his neck for his hypercritical caveman buddies to lop off his head if he is wrong about anything, he would absolutely be able to make a whole bunch of valid conjectures about the first 1015 positive integers, indeed, about all integers in general.
That's the power of sampling. It doesn't hurt us one bit that our sample is almost vanishingly small in comparison to the larger population. The only thing that matters is, is our sample representative? That's all I'm saying.
Our SETI data constitutes a very small sample relative to the larger population. But it doesn't matter. We can live with that. The only question is, is the data representative? I think there is a good chance the data are representative.
Make sense, or nonsense? :-)
One of the many things of radio astronomy I have no clue on is the ability of the telescopes to pick up signals on single planets within a solar system at any given moment. For example, if you point your telescope near a star does it have to be pointed exactly at the spot where a planet is to pick up a signal or do the telescopes have a wide enough signal berth in that area to pick up any signal from the entire expanse of that solar system while scanning one place?