VIE's private server allowed remote upload/download and command execution of any client without that user knowing. Very useful for when they found cheaters, could steal the cheat program from them without them knowing, and design the next client to prevent that.
Also with older Continuum versions, you could still pull off the remote uploading of files from users without them knowing. Now, I believe he added a few extra safeguards against that, but officially, sysops cannot force an upload/download from a client without their knowledge (ie: entering a zone and getting lvl/lvz/etc). Of course, officially, the newest prerelease of Continuum should have not sent the process list constantly to the server either (was only to be via a command request). Ekted noticed that one, and released his own little hack to prevent that on fix.dll.