Well, of course, it's the Drake equation. It had to be. While it is certainly reasonable that everyone has their own perspective and opinion about the likelihood of alien life, it is not reasonable to pretend that the "Drake equation" provides some sort of inside track.
The article, "Proof of Aliens Could Come Within 25 Years, Scientist Says", lays claim to Carl Sagan's "calculation" of N = 1,000,000, while Drake himself places the value much lower at 10,000. So with two orders of magnitude separating the "calculations", we're to believe that such speculation has merit because of the Drake equation?
I would suggest that one cannot legitimately claim the calculating power of an equation if the terms aren't defined. Therefore regardless of the results produced by the Drake equation, the simple reality is that it is ultimately no different than using a Ouija board to make predictions. It's not a theory, it's not even a hypothesis. It's merely a collection of terms that suggest what needs to be considered before attempting to establish a probability of intelligent life.
Of course, the most obvious consideration is that it might not even be remotely accurate.
Historically Drake used the following values for his calculation in 1961:
* R* = 10/year (10 stars formed per year, on the average over the life of the galaxy)
* fp = 0.5 (half of all stars formed will have planets)
* ne = 2 (stars with planets will have 2 planets capable of developing life)
* fl = 1 (100% of these planets will develop life)
* fi = 0.01 (1% of which will be intelligent life)
* fc = 0.01 (1% of which will be able to communicate)
* L = 10,000 years (which will last 10,000 years).
Drake's values give N = 10 × 0.5 × 2 × 1 × 0.01 × 0.01 × 10,000 = 10.
So I would suggest that before we simply plug in more numbers and do the calculations, let's test one of the most obvious terms in the equation. The third term (ne) indicates that of the stars with planets, two planets will be capable of developing life. This is clearly a testable hypothesis. We can use our own solar system. So I would suggest that before we start planning the dinner party we're going to throw for the first aliens, perhaps a more modest goal would be to see if we can find even one more planet in our solar system that has life.
That would be a sufficient factor in deciding whether the rest of the Drake equation has any possible merit at all. In addition, it would be a strong reality check on what finding an alien life form really represents.