Assess the risks
I agree with HypnoToad72 - you have to understand what terms you're operating under, what the SLA is - whether there are any Data Protection implications, and so on. Is there a chance they could lose all your data? Can you export it to do your own backup, just in case? What reputation does the service have for security and support? Just ask as many "What if?" questions as you can think of.
The same applies, of course, to non-cloud solutions. If you're backing up to USB hard drives, what if the disk fails? What if the building burns down? What if I take one home and it's lost or stolen? What if...? Having done all that, then decide which model works best for your business.
