Unfortunately, they are dealing with low probabilities. First I will address the possibility of our presence being detected. The probability that any civilization has detected our presence is very small. We have been emitting electromagnetic energy for about 100 years so the sphere of detection is 200 light-years in diameter. This is a very small part of our galaxy. The Milky Way Galaxy is 100,000 light-years across. Some studies have looked at the number of star systems within that 200 light-year sphere that are capable of having viable exoplanets and the number is small. Also, since signal strength drops off as the square of the distance, detection of any of our emissions becomes more difficult the further away an extraterrestrial civilization is. The best chances of detecting that we exist is via the transit method assuming that any civilizations capable of looking are in our orbital plane. Regarding our detection of emissions from other civilizations (what SETI is looking for), the problem of signal strength dropping off as the square of the distance will be a problem. The distances across our own galaxy, let alone the observable universe, are vast. From a signal to noise perspective, it isn't clear to me that SETI efforts are on a firm technical footing. However, I was part of SETI@home for a number of years. It was an interesting distributed computing effort.
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Originally Posted by ThirdOfFive
Yet, the SETI program continues.
Is it possible that the folks in charge of that program have a bit more insight into the possibilities of contact being made than either you or I?
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