Several people have asked about dropbox support, unfortunately dropbox does not have an official .net (C#) SDK. There are some 3rd party ones, like SharpBox (sharpbox also adds other providers) however they all require us to register the application with dropbox (which may be tricky) and use oauth for auth. Due to these restrictions the 3 current .net unofficial sdks seem out.
SkyDrive is a bit more friendly, it still uses oauth but does not require application registering with them. Unfortunately the oauth means that every time keepass is started up you would be prompted for your live login/password which is a bit of a pain to say the least.