Annoyingly, this also includes the codex and extensions gallery.
As far as I can tell, this is only the wordpress.com homepage (not the blogs they host) which is probably mostly unused.
blacking out all the blogs they host (i.e. protesting against censorship by engaging in large-scale censorship) would be incredibly uncool and sure to do more harm than good.
I agree completely, but my point is that what they're doing is likely to have little effect -- who goes to wordpress.com?
At least some of the 35 million people that host blogs there. They also censored wordpress.org, which Quantcast says get 8 million monthly visits. All in all, the number of people that see the message will probably be in 7 digits.
They could offer an easy "censor my site" option for sites hosted on Wordpress.com
they do.
Any WordPress.com site can protest by going to Settings → Protest SOPA/PIPA.