I don't mean to be an enemy of SETI, I find it fascinating to say the least, 
but an increasing number of scientific minds are growing more and more 
critical of the project.  I was severely chastised in these groups for 
merely stating the somewhat obvious.

I said that it was highly unlikely that efficient radio communication would 
contain repeating elements, which is what SETI is mainly searching for. Our 
own communications use a type of compression that takes out repeating 
elements, thus making it appear more and more like random noise.

I also questioned the logic of an advanced civilization using radio 
broadcasts into space as an efficient means of communication.  Particle-beam 
signals would be vastly more efficient, but much harder to detect by third 
parties such as ourselves.

Organisms in nature rarely broadcast their presence to the surroundings. 
Organisms on other planets presumably follow the same laws of nature too. 
Remaining incognito is what most organisms make great efforts to do. 
Exceptions are those who want to mate, and take the calculated risk, but I 
don't think any alien intelligence would be broadcasting radio signals into 
space for such a purpose.

And perhaps most important of all is the tiny window in the vastness of time 
and space that any intelligent civilization would be able to attempt to 
communicate with others in the universe.  The chances of finding a similar 
civilization to ours, beaming out friendship signals in hopes of connecting 
with another are probably as remote as two bullets colliding in the air, 
shot from different sides of a mountain, on any given day in a millenium.