Hm. Given that authors, critics, and reviewers tend to be from a leisure class, I think that the likelihood of author-critic and author-reviewer interactions hasn't suddenly exploded on a percentage basis, but I do think those interactions have become more accessible to people outside literary circles , because they happen in open forums rather than closed salons or the letters sections of lit mags.
Which brings up another issue with this democratization of criticism: because reviews and critiques can come from everywhere, rather than from a small selection of widely-read literary publications, authors may have less reticence about responding to them. It's probably a lot easier (psychologically) to hop on line and yell at a pseudonymous* internet critic than it is to write an angry letter to the New York Times about a bad review from Michiko Kakutani.

*Not to put down pseudonymity, but to contrast the effect of a pseudonym and a Big Name Critic on a hypothetical author.