I did a fairly in depth review of the Femi Paradox a few years back. The point of the Drake Equation is not only for intelligent species but for intelligent species with the technology to be able to communicate further out than their own little globe, or it not communicate as such, make enough noise for others to be able to detect them. A year or two ago I listened to a lecture in at Swinburne that discussed the distance of radio transmissions through space. What I got out of that was that our general radio pollution through the universe, although it has been happening since the 50's, becomes so weak and buried in noise that after about a lightyear it isn't even detectable. Even with purpose built powerful directed radio transmitters, we're still only limited to a few light years and even at that distance it would just be a very weak noise source.
As to the Drake Equation itself, it is pretty much a moot point. The first half of the equation has a scientific base that, through some research, can be calculated to defined values such as ~1.3% of stars within a defined region (not too close and not too far from the galactic centre) in our epoch have potentially habitable rocky planets [I think that was the value anyway, been a few years since I wrote it].
The second half of the equation however is just pure conjecture. For instance, there have been approx 100 billion species on Earth in the last few billion years so from that stand point you can say that there is a 1/100E9 chance of intelligent life forming (if you believe we are indeed intelligent life
). But that is not what the Drake Equation is asking for as you can either take the stance that the value is 0 in that intelligent life forming was a complete fluke of nature and that the 1/100,000,000,000 is a conservative estimate and that it is in reality so close to zero that we are the only intelligent life in the universe. OR you can say the value is 1 and take the stance that anywhere life can live, intelligent life is inevitable given enough time.
So, depending on your personal belief, just one of the values can range between virtually 0 and virtually 1. What is the chance of life forming at all? Somewhere between "impossible" to "it WILL happen if the conditions are right".