But this seems to me, at the very least, irrationally inefficient. You have a finite amount of time, and it can surely be put to use much more efficiently than verifying every single new fact and idea.

You're right, that would be highly inefficient. Now that you mention this, I realize part of what is attractive about reading blogs is that popular posts will tend to have lots of comments, and many of those will point out possible errors in the post, so I can get a higher certainty of correctness with much less work on my part.

Are you asking for an answer in everyday human terms, or an evolutionary explanation?

I guess what I'm really interested in is whether I'm missing out on something really great by not participating in more live conversations (that aren't about solving specific problems).