Save your summaries for techcrunch. They are not for refereed writing on subject X (i.e. 'existential risk') by the foremost authority on subject X. If you're not reading the whole thing (perhaps 2 or 3 times), you may as well not read it.
"So this is why I conclude that the silence of the night sky is golden, and why, in the search for extraterrestrial life, no news is good news. It promises a potentially great future for humanity."
This HN submission actually isn't even all that bad as far as it goes; check the comments on some of Bostrom's submissions to other, more popular, fora and you'll be routinely smacking your forehead.
EDIT: Sorry to be the bearer of bad news, here - not everything worthwhile comes packaged in a ten-sentence blog post.
Therein lies the real problem.
See in particular the most recent paper from NASA (November 2009):
Life on Mars: New Evidence from Martian Meteorites
"New data on Martian meteorite 84001 as well as new experimental studies show that thermal or shock decomposition of carbonate, the leading alternative non-biologic explanation for the unusual nanophase magnetite found in this meteorite, cannot explain the chemistry of the actual martian magnetites. This leaves the biogenic explanation as the only remaining viable hypothesis for the origin of these unique magnetites. Additional data from two other martian meteorites show a suite of biomorphs which are nearly identical between meteorites recovered from two widely different terrestrial environments (Egyptian Nile bottomlands and Antarctic ice sheets). This similarity argues against terrestrial processes as the cause of these biomorphs and supports an origin on Mars for these features."
http://www.nasa.gov/centers/johnson/pdf/403089main_7441-1.pd...