Failure to have a search function as facilitation of infringement?

An interesting statement in the Megaupload indictment:

It was further part of the Conspiracy that members of the Conspiracy had the ability to search files that were on the computer systems they controlled, and purposefully did not provide full and accurate search results to the public, or, in the case of Megaupload.com, chose not to provide any search functionality at all in order to conceal the fact that the primary purpose of the website and service was to reproduce and distribute infringing copies of copyrighted works for private financial gain.  

I recall similar arguments in Viacom v. YouTube: YT's terrible search functionality made it difficult to find all the infringing clips at once.  Given that there are good reasons to have nonpublicly searchable sites or areas in a site, how far does this argument go? Dropbox, which I now use, doesn't as far as I know have a search function at all, because it's designed for limited sharing circles, though one can generate a public link to a specific file and share that link.  While Megaupload is alleged to have done plenty of other stuff to facilitate infringement, it's a little worrisome that "failure to allow any random person to rummage through a user's uploaded files" might be taken as "evidence of intent to conceal copyright infringement."

NB: I have in the past used Megaupload to share my class notes and slides for Copyright and Trademark, though I now use Dropbox for the same function.