I think that there is consensus that the big players all need a better offering. They all need to be able to offer 'cloud' as that is the fashion, so CIOs don't want to be shown up at the golf club by not being into cloud.
The problems identified by others are also real; security, latency, availability. Whatever the actual security of a cloud storage provider there will always be a perception (sometimes shared by auditors) that it might be less secure than on-site. It is the same logic that makes people put cash under the matress rather than in a bank.
The network connection from your data centre to the cloud storage will break from time to time; arguably that also means that your users likely cannot access your servers anyhow, so you will have made a plan for that. As noted by others, for some applications five-nines availability is not required so cost will be the main factor.
What a smart cloud provider may be able to do for you more cheaply than you can do yourself is make your data available to another of your data centres, so you just fail over your application. But if you were doing that, wouldn't you put the application into the cloud also?
I'd suggest that the big vendors will blur the distinction between storage - virtual SAN using in-server disks, on-site flash for the small % of data that is 'cached' in your data centre, and cloud for everything else. They just need to find a way to put one badge on all of it, rather than coming at you with lots of product names and even company names.