Dropbox uses (used?) Crocodoc to do its document previews, which would be interesting now that Crocodoc has been acquired by Box (a Dropbox competitor). Crocodoc actually ran full Windows VMs to have Word interpret Word, unlike what was speculated elsewhere here (using LibreOffice) - it turns out pretty much everything else sucks pretty badly at rendering Word docs, largely because the format is a bloody nightmare of binary encoded blobs including OLE embeds, etc. My understanding was that these VMs were run on AWS Windows instances, which explains why the document was seen opened on an AWS cluster. I know they had a fun nightmare of a time getting the right licenses from Microsoft to do this.
