Gordon Weakliem makes a point that should have been obvious, but wasn't (at least to me):

As someone pointed out in the comments, you want this information to be accepted and managed by a third party (e.g. a regulatory agency), not managed by the company itself, at least for the financial filings. How about for press releases and the like - not-regulatory filings, but still material data? For similar reasons, I don't think that simply publishing to the web is sufficient in itself. I can name at least one popular blogger who's been taken to task for modifying or deleting postings and has been accused of "rewriting history" for doing that. There's certainly the potential for that if a corporate weblog were the exclusive source for those releases.

This is in reference to my earlier post on this stuff.