You might find this article interesting:
ESO - eso1134 - Fifty New Exoplanets Discovered by HARPS
Especially this part:
#Thread:
We can't just discard any possible option with no proof whatsoever.
Before you get too optimistic about the possibility of life on other planets, you should have a look at this article. Yes, it's a bit old, but the facts are still true, any slight variation from the orbit Earth has would not support life.
It's in the first column on the left.
The Dispatch - Google News Archive Search
"At a distance of 93 million miles from the sun, earthly temperatures have supported life. But if our earth had been slung into an orbit only 5 percent closer to the sun, a runaway greenhouse effect would have turned the planet into something like Venus—a cloud-shrouded planet with temperatures close to 900° F."
That narrows down your search for habitable planets a bit. And then there are atmospheric conditions to take into account. And beyond that we need to look at the soil/surface of the planet. It really makes you realize how special Earth is.
Heh, Norton, an Anti-Virus? It is the Virus!!! Get rid of Norton!
One last point: If there really were highly advanced tangible extraterrestrials in the universe, would it be reasonable to conclude that they would have already sent out exploring parties looking for other life? Perhaps some would have settled on our planet already, become addicted to Tibia, and have been posting here for a couple years...
Another point from that article stated that the minimum amount of time a planet needs to have temperature stability, around 3.6 billion years, is another factor that needs to be considered when looking for other life. I think some people have become overly optimistic about the possibility of life elsewhere as a result of watching sci-fi films, and they forget the basics of what life needs to survive.