From Phil Plait's blog (http://mblogs.discovermagazine.com/badastronomy/2011/03/05/h...), the journal is closing, albeit after a conspiracy-soaked rant: http://daviddobbs.posterous.com/journal-of-cosmology-going-o...

Long story short: take this paper with a pretty large grain of salt.

TBH I'm more interested in the social impact evidence of alien life would have, rather than the scientific one.

Evidence of panspermia early in Earth's history would be interesting, but I am not sure it would actually teach us much. OTOH there would be significant implications for some major religions.

Religions would only be impacted by intelligent life. Bacteria and even higher animals would not do anything.

Pfff. Religions are flexible. They will cope with everything you throw at them. They must be, their lifetime is measured in centuries.