This might be one of the last comments I make before these charges come in, because I won't be paying. There are too many places I can vent my spleen for free.
It's ironic, really, that The Register wants to charge users so they can contribute to the site... as in "you make our site more interesting, and we charge you for the pleasure. double bonus for us!" Still, I think I can guess how interesting the forums will become after the charges are brought in.
Speaking of accessibility, I'd suggest a charging policy will make your forum less accessible (specifically to those who aren't subscribed and don't want to pay). And it's interesting to see El Reg wheel out some of those sickening spin lines so often seen in government press releases.. "to make it more accessible and satisfying for you to use". Yeah whatever!
Final thought... how many entertaining stories have you published about some random nutter posting utterly bizarre comments? I guess you'll be saying goodbye to those, as well.