Pretty big assumptions, indeed. Why couldn't conditions exist for life to begin early in a planetary system's lifecycle, such that intelligent life could develop early on and potentially survive for many billions of years?

I tend to think that life is very likely abundant throughout the universe, in very simple forms. If the origin of life on Earth is panspermia, then it stands to reason that the same life that "contaminated" a proto-Earth is likely to have been propagated to other worlds as well. More complex forms are certainly less abundant, and "intelligent" or sentient creatures are probably fairly rare (though "rare" is a funny term in relation to the size and age of the universe). The number of systems supporting life capable of detecting other systems supporting life, however, is probably damn near zero (we can't even do it at this juncture - we can barely detect other planetary systems, and our methods are largely through indirect observation). So I would contend that it's a reasonable position to suggest that intelligent life is not unique in the universe, it's just that the obstacles of the vast expanses of time and space make it nigh-impossible for any of them to ever detect one another, much less contact one another. It would take superluminal travel technology in order to bridge those gaps, but even FTL travel doesn't help you figure out WHERE to go look for other life.

Zif, your point about life self-destructing is summarized in the Drake Equation popularized by Carl Sagan.

The Drake equation states that:

N = R^{\ast} \times f_p \times n_e \times f_{\ell} \times f_i \times f_c \times L \!

where:

N is the number of civilizations in our galaxy with which we might hope to be able to communicate;

and

R* is the average rate of star formation in our galaxy
fp is the fraction of those stars that have planets
ne is the average number of planets that can potentially support life per star that has planets
fℓ is the fraction of the above that actually go on to develop life at some point
fi is the fraction of the above that actually go on to develop intelligent life
fc is the fraction of civilizations that develop a technology that releases detectable signs of their existence into space
L is the length of time such civilizations release detectable signals into space.

Basically the "L" term in that equation takes into account how long an intelligent, broadcasting civilization survives. In our case, that's less than 100 years, really. That means that any signals we've sent out could only possibly have reached stars less than 100 light-years away. Even if we went on to survive as a technologically capable species for thousands of years, any system within a radius that could receive those signals would be receiving signals thousands of years old. Even if they could get here or respond, they (or their signal) could still arrive long after we're all dead from war or natural catastrophes.

The hilarious thing about Soy's article is how long it is, and how many people the author felt compelled to include in order to overshadow the dumb hick waving his arms and shouting, "It was me! I did it! It was just a big joke! No aliens over here..." Was it really necessary at that point for the Air Force to deny any involvement? Like the Air Force is "involved" with some redneck tying road flares to helium balloons? Or some astronomer saying "I believe in aliens, but why haven't they abducted me yet? I like getting anal probes!"