The comics piracy scene is huge, and the industry is well-aware of it. Thankfully, the publishers have not taken a leaf from the book of RIAA and sued their most avid fans. The downloaders, for their part, offer the usual litany of excuses -- that they sbuy the comics too, that they're waiting for the trades, that they buy other comics, etc. (In my experience, though, they're actually telling the truth. But that's another story.)
What really makes the SLG announcement notable is that the comics aren't in some closed, DRM-infested proprietary format: they're
.cbz files. Not only is it an open format -- it's just a
.zip file with a different extension -- it's one of the two main formats used by the scanners.
And for whatever it's worth, some of the larger comic-trading communities have banned those issues from their hubs and trackers now that there's a legitimate alternative.