Before those cloud storages were popular, I stored all photos in multiple HDDs, 2 years ago, started 80G space from Google Drive, I store photos in the Google Drive and have sync copies on my 2 notebooks, furthermore, I run backup regularly on one of the notebooks which includes the sync Google Drive folder.
Cloud storage is in big data centers. Users buy or lease storage capacity. This is the "paid for" model.
loss of service if cloud has technical problems and temporary downtime.
cloud operator winds up and goes out of business.
little or no cure if there is a big technical glitch/fire that causes data centre to lose your data.
Data insecurity - don't store sensitive/secret information/photos in the cloud storage.
And the above is just for the "paid for" service.
If it is FREE cloud storage, cloud storage operator don't owe you anything and can pull the plug anytime - permanent data loss.
It costs money to buy equipment, setup up, operate and maintain cloud data centres over the long term.
They may not be able to afford to give you free cloud storage (of a small limited GB size) forever.
At some point, they need to charge you money.
Free cloud storage is an enticement to introduce you to their cloud data centre service; so that you will upgrade to a regular paid service agreement later on.
One can only choose the "best" option based on budget and tolerance of the limitations.
If cloud storage is not within consideration, an alternative suggestion to HDD backup, is to get a good and reliable NAS box with NAS-grade or 24/7-grade hdds. Run at least in mirror configuration, if not RAID 5/6 or better.
NAS boxes has come down a lot in pricing as more and more manufacturers introduce almost enterprise-grade offerings at consumer prices. Anyone remembers that NAS was 5 to 6-figure pricetag per box? ;p
But NAS boxes comes in a variety of options and settings, although some are easy to set up, some are more technically challenged. So always get a friend who is proficient to help you kick start in getting your reliable backup storage.
the 3 popular cloud services from Dropbox, GooogleDrive (provided by Google) and Skydrive (Provided by Microsoft) all have the facility to keep a sync copy on as many computers' local drive. Once setup, you treat it like any local files in your computer, you can open, edit, and continue to update the folder, and once the computer is connected to Internet, it will automatically update the cloud storage as simple as that.
And if you have more than one computer, you can setup the local copy sync in more than one computer called Com A and Com B: you make changes, add more photos in computer A off-line, once computer A is connected to internet, it will update the cloud copy and later when computer B is also on line, it will also be updated. If you lost both computer, you can still access the cloud copy and if you are not on-line, you still can access your photos directly from your computer locally. Better still, you also do a external drive backup of your computer, in this way, you have your photos in 2 computers, cloud and backup drive, and operation is so simple and seamless.
Another advantages is that, the cloud storage also keep track of files deleted, and few old revisions of file for you.