"Remember LOKI, the prolific poster who'd get his/her shorts in a wicked twist any time someone posted that maybe, just maybe, Earths or intelligent beings might not be commonplace? LOKI would post long diatribes re-stating long standing arguements of denial. Get really emotional. Rarer than rare Earths have been such replies by others for several months. Unfortunately, the only remaining proponents of plentiful ETI are the UFO cultists who see alien spaceships in every flock of geese."

As I recall it I gave some SWAG of 1000 intelligent civilizations in this galaxy and LOKI seemed to be "happy" with this number.
I think that you think (and Mark Eby thinks) that 1000 out of 200,000,000,000 does not qualify as rare enough.
Just for fun I'll put some numbers on common and rare:
Very Common- for example dozens of different aliens visiting Earth, MIB type thing: 1 billion+ intelligent civilizations.
Common: In range of 1 million to 1 billion civilizations
Rare: less than a million.
Very rare: less than 1000.
Unique: Earth has only intelligent technological species called Human.
Note if we are unique to this galaxy I would say then the odds would slightly favor that we are also unique in the entire Universe- unless there was a God (or something functioning as a god) which was placing one intelligent species per galaxy.

Now what exactly qualifies as an intelligent civilization. Or a similar question is when do we qualify as intelligent civilization. Were we an intelligent civilization a million years ago? 100,000, 10,000, Apollo landing, or have we yet to be qualified as an intelligent civilization?
I would say from a "Universal perspective" that an intelligent civilization is one that is attempting to have a "relationship" with another "species".
Using this definition we can place roughly in time when human started to become an intelligent civilization- about 20,000 years. Physical evidence of this is seen in cave art and burial ritual. We domesticated animals and worshipped various things.
Now how do you "count" intelligent civilizations. As far as is currently known there is one intelligent civilization- Humans. Now, let's get out of the box and do some imagining. Could dolphins become a intelligent civilization? I mean with our help, could we learn their language and/or teach them our language? Could we educate them- have them wear "wrist watches" and show up for work:) If this happenned could you count 2 intelligent civilizations in Sol system? Or instead of Mars being a frozen desert, say it was instead a another planet with a robust bio-sphere with inhabitants which were less advanced than ours. And say after much hand wringing we decide that rather than exterminate/enslave these dumb creatures "we work with them". Again, could this count as two civilizations?

Now, assuming physics remains roughly the same as our current understanding, who, why, and when will we colonize the stars? The idea of some huge socialistic bureaucratic government systematically planting the heavens with colonists seems pretty strange to me. I think it's possible but doesn't seem probable. I think it's unlikely that this will be attempted, and if attempted, almost a certainty that given enough time, number star systems, and distance it would fail- and fail Big Time, making the Great Depression look like a minor "economic slow down".

I see 1000 civilizations in this galaxy as a fairly conservative number- half of this number would be civilizations which had some connection with other civilizations- social and/or biological, recently/currently "connected" or had history of connection. The other half like us- isolated.
I think it's quite possible that there are more than 1000- if there is more it's likely it's a result of intersellar travel- meaning more civilizations will be in specific parts of galaxy- like cities. Another "way" there could be more is how you define civilization. Or way it could be less than 1000 is how strict you define civilization- the major "players/influences"- and we might not even be counted in this tally.
-gb