Oh Those Missing - Read: Purged - Emails

Anon posting in Comments on my original post about this the other day points us both to this post at Citizens for Responsibility and Ethics in Washington's blog as well as the comment available below this post. Here's the main post:

LIke most observers, the editorial writers at The New York Times are finding it difficult to understand why the Bush administration and the RNC can't find all the e-mails from White House staffers. The Bush administration had a legal obligation, under the Presidential Records Act, to preserve those communications. That seems not to have been a concern:
    The post-Watergate law requiring the preservation of presidential records has proved to be no match for the Bush White House’s stealthy use of back-channel e-mails via the Republican National Committee’s computer system. Congressional investigators have discovered that while 88 White House staffers had accounts over at the G.O.P. computer banks, there are no e-mail archives to be found for 51 of them.

    Congress has demanded that the White House and the R.N.C. provide the full e-records as it tries to figure out the story of the political purge of United States attorneys. Claims by the White House and the R.N.C. that they’re trying their best to comply are increasingly hard to believe, and we strongly urge Congress to continue the search.
We strongly urge Congress to continue the search, too. Strongly.
Now here's the comment on online collaboration:
We disagree with the NYT emphasis on e-mails. Based on Ralston's denial, it appears there is something else going on.
    Question: Karl Rove didn't discuss this claim with you?
    [Ralston, response]: No.Mr. Berenson
    [Ralston Counsel]. Do you want to clarify that last answer?
    Ralston. I don't recall. I don't have a recollection of anyone discussing with me specifically that claim.
Ralson leaves open the possibility that the GOP and WH-EOP have an online collaborative file sharing program such as SharePoint, which integrates with MicrosoftOutlook. However, this is a third-party website, which RNC could hide, say it is not a file system they own, and avoid providing it to Congress. What review has Congress does on online collaborative file sharing programs which are not related to e-mail, but could fit nicely within Ralston's denial above?