I'm not sure that I would say that it "doesn't matter" (indeed, further down the article, Greenspan admints "there's no evidence to suggest that changes in margin requirements ... had any effect on prices." -- to the contrary, it rose 25% despite the market "only" rising 11% -- so how exactly is this contributing to a speculative bubble?), but this seems like it was $50B borrowed by individuals.
Ok, so the Fed is concerned about margin. So? Don't leave us hanging. Tell us what the WSJ article didn't tell us that's on your mind.
/jordan