Sure, you could cynically say that because of DC holding their titles at $2.99 and dropping the story pages down to 20 they want us to provide them with free content but I really don't hold with that. I'd rather pay a little less and still have something to read, myself.
I had a couple of letters printed in comics in the old days - definitely one in Preacher and one in Martian Manhunter (both complaining about the same sort of thing if I remember rightly) and possibly one in Justice League America around the Dan Jurgens era. Seeing your name in print at the back of the issue you've just read was such a nice buzz which can't be replicated by typing something on a message board and pressing submit.
How it'll work, what with the immediacy of the internet, blogs and the DC message boards (isn't it about time they updated those? They've looked the same for years) is yet to be sorted out but I did note one thing Dan Didio said in a CBR interview about this:
We're looking at the letters pages too as a place where everybody uses their real names. We want people out there to be identified so we can see who our fans are. It's not going to be anonymous because we really want to have that sense of community where people are meeting each other, knowing who they are and enjoying the comics together.It's so easy for people to badmouth each other and basically be rude on the internet, hiding behind anonymity or nicknames, so it's good to see that it'll be real names only.
And on a side note, check out the image at the top which DC used to publicise this news story. Batman, Wonder Woman and Superman are there, as you'd expect, along with Green Lantern and Flash but no Martian Manhunter which would round out the Big Seven. Instead we get a couple of mid-list heroes, including Power Girl - nice to see her being used in such a big news item!