What's this have to do with the OP? 

I'm a pretty nice person. I wouldn't do these kinds of things for the hell of it. However, if a friend pisses me off or if they catch me having a very bad day, my thumbs might accidentally twitch, access the cloud save and delete it.

Im still waiting for the offline fix for this same issue, friends coming over to your house, trying out your game and deleting your savegames is a stupid security hole thats up the manufacturers to fix.

But whats even worse is, when theyre at your house they even have the ability to change your passwords or format your machine completely like that! nintendo microsoft and sony are soooo sloppy!

(kinda hoping you detect the sarcasm and in doing so realize how ridiculous you sound calling this a psn security flaw)

It's like VGChartz!

There are no bugs or flaws in the system, they're features! Features, I tell you!

What if I want my friend to delete my save files? Gives me more time to play. :P

I figure i may as well state this, since some people seem oblivious.
You cannot go into the ui and delete any old save, and this is only possible on games that use their own savegame management system independant of the consoles OS, if the game attempts to save using the OS management, control via remote source is cut off and handed back to the owner.

But more to the point, theres nothing stopping you from logging in to a new user account on your own console prior to letting an untrusted friend play, and if youre letting a "friend" take control of your main accounts game progression, and they use that to mess up your game, then you probably shouldnt be making friends with douchebags.

I unknowingly deleted my friend's Mass Effect 2 save to download Mass Effect 3 onto his Xbox....the cruel cruel irony.

It's so totally out of order that Sony should offer this feature, the world is a dangerous enough place without Sony adding to it, world peace could be threatened! A leader from one country share plays on another leaders PS4 and deletes his game save, it could lead to an international incident, there could be war, thanks Sony for ending the world!