There are several interesting articles about SETI and extra-terrestrials in the november issue of Ciel et Espace.

The Copernician approach (the Earth is one planet out of billions of others) would suggest there are many extra-terrestrial civilisations all around us...(the banality principle if you want: we're not alone and neither are we the firsts).
This approach has become a nightmare to SETI scientists.
There is the Fermi paradox: they must be here but we don't see them!
The problem is the immediate visibility argument. (The ETs must be obvious to us).
It reduces the quest for an intelligence to a foreseeable (expectable) phenomenon. However, intelligent behaviors are everything except expectable, as witnessed by the history of anthropology and sciences.
Seti is however conditioned by absurd reasonings such as a gradual history of civilizations going from less evolved than ours to one like ours. This is ignoring cultural diversity and innovation. We all belong to the same Sapiens sapiens family and yet history of cultures on Earth is very complex.
Can we even hope to communicate with a more advanced civilization (several million years ahead)?