Over at Classical Life, critic Tim Mangan's blog, Tim has picked up on a point from my Blogging Basics page. An interesting discussion has ensued, with a range of readers weighing in, including the illustrious Martin Bernheimer.
My own experience is that classical music bloggers will, eventually, hear from performers. I certainly have, and I listed some of those I've heard from in my comment at Tim's. I should note that to my knowledge I've never reviewed one of flutist Tod Brody's performances; I've reviewed many SFS and SFO performances in which Carey Bell played. (Some day I'll catch up with them both at SFCMP.)
I'm reasonably sure that in part it's the informality of the medium, in part because some performers who wouldn't necessarily write to, say, Anthony Tommasini or Joshua Kosman with a complaint are perfectly willing to write to a blogger or comment on a blog. We're not always regarded as legitimate reviewers. I had one intense email exchange with a performer in which the performer asked me about my credentials - and then dropped the discussion.