Do you have a link to the reports? Python and Go seem to be used a lot at Dropbox. Blog post on their Go usage: https://blogs.dropbox.com/tech/2014/07/open-sourcing-our-go-...

I could only find two Rust repositories on their github page, both of which are library bindings forked from other projects, so that seems to indicate some Rust usage. But then again there are more Haskell repositories than Rust repositories: https://github.com/dropbox