I agree with that, provided there's no crossover possibilities.
One potential risk is that if a mobile device has the ability to upload, that the end up uploading domething you didn't intend to by accident, especially if folder-syncing. If you don't have software, or account/password details, on the device, then short of a malware infection, it won't get uploaded by mistake.
Ultimately, this sort ofcquestion always comes down to a balance between the risk of compromise and the possible damage if it happens, on the one hand, and the benefits and convenience on the other hand.
I have one mobile device which contains, among other things, backups of a secure online facility containing client company board meeting minutes, bid proposals, etc. They are there at the company's request, for their benefit, and with their knowledge, but part of the implication of my contract is that, ehole a tisk is inherent in having those files on the device, I do have a legal duty of care to keep them secure. If any mistake on my part, such as putting the wrong file in the wrong place, or having the wrlng settings on the upload software, resulted in a contract loss I could potentially find myself on the wrong end of a lawsuit ... and one that could and likely would cost me my house if I lost.
And that's just one of the potential business risks.
There's nothing "paranoid idiot", as Torashin put it, about not taking unnecessary and potentially hugely expensive risks for little or no gain.
Clearly, that's not a risk most people will run, and clearly, the risk is very small. But small or not, it's a potentially ruinously expensive, life-wrecking risk I simply don't need to run. And yes, I run encryption software, etc. So it's not likely to happen, but nor am I likely to have a fire that burns my house down, but do I want to be without home insurance that covers fire? Hell, no. The benefits (saved premiums) don't justify the risk (loss of home I worked for years to get). Ditto uploading to the cloud. It's just not worth it for me.