SaaS or any other cloud based service model. Storing your data somewhere else where it gets held hostage in a proprietary format is a lot of pain waiting to happen.
Dropbox and Gmail are examples of how it should be done, I have a copy, I can make more copies, they make sure its accessible from everywhere I want. If Dropbox or Gmail suddenly stops I will still have my files.
> "Storing your data somewhere else where it gets held hostage in a proprietary format is a lot of pain waiting to happen."
Which isn't really all that different a situation from having your data held hostage in a proprietary format on your own machine. And now we all sound like RMS.
Somewhere along the line, most people draw a line between security and convenience. Some will get burned by this line. Others will appreciate the risk, plan accordingly and come out ahead for having had a fallback and profited from the convenience in the meantime.
It's harder to say where a reasonable exchange has been met when it comes to media. But for things like, say, Twitter/Facebook/LinkedIn or even SaaS offerings like Salesforce and such -- who's to say a user wouldn't have gotten acceptable value from it before its inevitable end (or a change of terms such that the user won't get any more value than if it was simple closing forever)?
So, for most, the "pain waiting to happen" isn't, by itself, a deal-breaker. It's simply a cost that ought to be considered, but no different from any number of essentially-unknowable surprises this world saves for those who dare to make long term plans.
It obviously is, but you're only trusting the 'cloud' to keep an extra copy and help you maintain synchronization between your copies. If they go down or out, you've only (potentially) lost the latest changes if you actually threw away the machine you were sitting in front of when you made them. In other words, good use of the cloud.
*edit: So they provide sharing and cloud sync, too. I'm not sure if that should detract. I haven't used Dropbox shared folders since they were Public Folders.
SaaS etc... however is, which I assume you mean? (sorry for trying to be a smartypants!!!)