In no particular order:
Drakes first equation attempted to estimate the frequency of technically identifiable species only, specifically radio-using species. this includes terms for the probability of a species wiping itself out as well (although I'm no sure it contained a term for ecological suicide). This still produced and estimated 10,000 technical species at the present time (that is, not total over the lifetime of the galaxy)
Drakes second equation attempted to estimate the diffusion rate of SITAPH's given a maximum velocity of 0.5c, and concluded that our entire galaxy should have been colonised several billion years before the earth coaelesced.
I disagree that looking for radio is a resort to the anthropic principle. The fact that we find a tool useful, or discover something about the world, does not imply anthropic projection simultaneously. If we are an evolved species without divinie intervention, governed by physics, then the opportunities that we discover should be discovered by other beings similar to ourselves. Radio is not a human invention, it is a discovery. The properties of radio are suitable, at least as far as we are able to determine, to interstellar communication. There may well be BETTER technologies we do not understand yet, of course.
On colonising and interstellar war, I do not think that presently habited or "biological cradle" planet would be at all attractive to interstellar travellers. This is because a species that can cross interstellar distances has already had to solve the problems of permanent space habitation, and does not actualy NEED a biological planet. It would be much more logical for them to park next to Jupiter and simply hoover up what resources they need.
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