For anyone who can't tell EP frequently makes mistatements about the impact threat see:

http://impact.arc.nasa.gov/
click on government reports to find the NASA sponsored studies, the more recent British report, and congressional testimony.

EP's nutjob claim that a lunar observatory is a low cost option for finding smaller impactors can be debunked by a combination of those reports and the reports at
http://rasc.larc.nasa.gov/rasc_new/rasc_fy01_top/CAPS_Top_page.htm

These guys are actually working on evaluating a lunar option along with orbiting telescopes. Off course, EP would prefer you read the condensed news version which totally ignored the advantages of orbiting scopes over lunar ones which the full report makes clear. Larry J did an excellent job providing extra background on this work earlier at:
http://www.habitablezone.com/space/messages/17247.html

It should also be noted that even objects as small as 300 m can be fairly well inventoried over several decades using existing scopes. The value of improved systems is not relying on the law of averages to protect us over that period, getting timely warning of even smaller impactors, and in detecting long period comets. See reports above and:

(H=20.5 averages about 300 m)
http://cfa-www.harvard.edu/iau/lists/Sizes.html
http://neo.jpl.nasa.gov/neo/number.html
http://cfa-www.harvard.edu/iau/lists/Amors.html
http://cfa-www.harvard.edu/iau/lists/Apollos.html
http://cfa-www.harvard.edu/iau/lists/Atens.html
(EP obviously failed to check or forgot the lists above when he claimed only 2 NEO's < 1 km had been discovered)
http://neo.jpl.nasa.gov/neo/pha.html#close
http://www.brera.mi.astro.it/sormano/sael.html
http://www.nearearthobjects.co.uk/downloads/02.pdf

Regards,
Mark

PS And no EP, I didn't call you a liar. I'm not sure whether your misleading comments are due to dishonesty or stupidity. Pure ignorance is not an excuse as you should have read all of these reports & sites if your dedication to the impact cause is what you claim.