Maybe I’m off the mark but it looks like Gabe has given memeorandum a bit of a tweak.
The page I’m looking at now, for example, has about 40 discussion links on the big FON story and nine of those stories are broken out so you can actually read the first par. To me it looks like Gabe has both increased the number of sources but is also exposing more of the “conversation”.
And I could be wrong with this one too, but I get a sense that memeorandum is now doing more analysis of a post’s content. This was backed up by a couple of remarks Gabe made in recent interviews, as well.