In all fairness, Rossi generally would not be able to use statements made by him on his blog as they would almost certainly be hearsay. Hearsay is, generally, an out of court statement being introduced to prove the truth of the matter asserted. If Rossi said something on his blog or in JONP and wanted to introduce that at trial to prove something, that would probably be hearsay and not admissible.
I am not a lawyer, but (in part due to fogbow, plus a lot of corporate contract stuff) I think that a blog COULD serve a useful legal purpose.
My understanding is that if you have contemporaneous notes on some subject, when you are being questioned, that you can refer to and read from these notes during a trial ... and that having them gives greater credibility than just recalling from memory.
So information in the blog, as a set of contemporaneous notes, could be used in a trial. They themselves would not become part of the record, but what the witness said about or read from, would.