With a shell account like one of these http://shells.red-pill.eu, I would like to schedule chron jobs to backup from Google Drive to SugarSync.
How secure are those servers? Can some obscure admin steal my Google/Sugarsync passwords?
The admins can get to any file you place on your account, if they want, including those containing passwords.
But since you are already trusting a cloud service with your data (two of them, it seems) you might as well go 'full force' and proceed.
If you want a backup solution where all the knowledge required to access and decrypt the file is in the hands of the client, but all the storage responsibility is in the hands of the server, and the server cannot do anything with the data it is storing, you may want to investigate tahoe-lafs, although it's different and will take a while to learn and setup.
I think a good rule of thumb is "don't use a system if you don't trust the system administrator."