Re: Whee are the aliens?
Life might indeed be common in terms of simple or non complex life like on the microbial level or such. And there might be worlds teaming with complex life on the animal level like Earth of the past before the rise of human intelligence and human civilization. The rarity mightn't be in life or even a measure of intelligence, but in intelligence giving rise to advanced technological civilizations.
Possible, but you also have to take into account 'deep time'. Even if there have been many intelligent civilisations within detectable range, over the (pretty unimaginable) length of time they could have developed in, the chances of them evolving at the same time as us (or at least at the right time for us to have picked up their traces) are very very small.
Soon oh soon the light, Pass within and soothe this endless night, And wait here for you, Our reason to be here...