from
http://academic.depauw.edu/aevans_web/HONR101-02/WebPages/Fall%202007/Craig/Contact%20Website/Pages/aliens.html

Read the whole citation, it is worthwhile.

An excerpt:
Ms. Arroway argues for SETI: “If we fail, we learn something of the
rarity of intelligent life.... And if we succeed, we hit the cosmic
jackpot. There's no greater discovery you can imagine.” (57) She also
points out that there's something we can learn instantly, just from
contact: that civilizations that build radio telescopes don't
immediately blow themselves up soon after. These are just a few of the
reasons to keep searching given in the novel. Sagan has argued for many.
Among them, he says that scanning the sky can lead to discoveries of
many sorts, even if none of them are intelligent. He points to pulsars
and quasars as two examples of phenomena accidentally discovered by SETI.

Once the Message is received and the world knows that they are not
alone, the question then shifts from "who is out there" to "what are
they like". The situation changes depending on the system. For example,
the Argus scientists correctly hypothesized that there were no proper
Vegans, since the star system was too young and filled with debris. The
broadcast must have been engineered from a source that had set up a
transmission station in Vega. (An example of didactic science fiction in
action.) Based on that, it was conceivable that the civilization they
had encountered was far more advanced than their own. Ellie argues that
this is extremely likely for any contact. Humans have only had the means
of communication (radio telescopes) for a few decades. If the
extraterrestrials were any younger, they'd have no way of contacting us.
It would also be extremely unlikely that they'd be at the exact same
level of sophistication as humanity. Therefore any contact would be
likely with those more intelligent than ourselves. Beyond that, it's
hard to predict the technology levels of any extraterrestrials without
either meeting them or having them send us some schematics for a highly
advanced engineering project. ---