I only use my machines to log on to services, can't bring myself to trust anyone else's machine.

Unless that VPS you run Owncloud on is hosted on hardware you have under your own control, it is not on your own machine. The acronym VPS ('virtual private server') is a bit of a misnomer as it is not as private as it may seem since anyone with access to the supervisor will have access to your virtual-not-so-private-server.