When I talk about a specific situation being "fair game" for blogging, perhaps one can say that courtesy implies a ritual exchange of asking permission and having it granted--in other words, "asking permission" in the second sense above. Whatever. I would prefer a world in which faculty feel comfortable engaging in discourse about ideas rather than feeling they have to go through some mutual grooming exercise beforehand, but others clearly disagree.
Still, in terms of the idea of what is genuinely within a speaker's discretion to squelch public commentary about, I am surprised at how some of the commentators regard things as private that seem to me obviously not private. While I still believe in the basic heuristics that anything that can be put on a CV is fair game for blogging, I think three other heuristics are even harder to argue with, although maybe one can say a person should "ask permission" with the presumption it will be granted:
1. If a talk is fully open to the public, it is fair game for blogging.I mean, come on. Again, none of this means people should not be "polite" in offering criticism of others' work, etc..
2. If a talk is open to individuals with media credentials, it is fair game for blogging.
3. If a talk is recorded and made available publicly on the Internet, it is fair game for blogging.
More generally, I think another way I diverge from the other commentators is that I'm not just concerned about what's right for the speaker. The academic blogger wants to write about something because they have a reaction, and their prerogative to be able to share that reaction with others should not be regarded lightly.