One aspect that is overlooked here is the actual safety of your data. If you feel that your own server has the safety and backup resources of e.g. Amazon (which Dropbox uses), you're probably deluding yourself.
Backup is irrelevant, you can always encrypt it and send to S3. As for safety, well, at least you're a considerably less visible and worthy target than Dropbox. And you can implement systems (e.g., stronger authentication) that Dropbox might disregard since they're targeting a less technical user base.
Personally, I use git-annex as my sync server, and all non-local transmissions are done over SSH using public key authentication, which is something that Dropbox will never implement.
I'm not arguing that you can't have a private server that's secure. I'm arguing that setting up an OwnCloud box is probably more insecure than using Dropbox.
You can manage your own backups, and then you don't have to feel how safe your data is, you can know it.
If you aren't worrying about petabytes of data, you can run your own scheduled backup, take a copy off site, and test it regularly.
With Dropbox, you're right that they have more overall resources, but you also have no way to audit their processes. Other cloud services have lost people data. If you want to be secure in your data, you need a way to audit those processes, so you would need to do it yourself anyways.
If I know I have a known good backup in a fire resistant box off site, I know I'll have access to that data later. If I have data in Dropbox and then the next day it's gone and they don't return my inquiries, that's a possibility. Maybe they get shut down without warning for hosting copyrighted materials like megaupload. Maybe they have been cutting costs by gambling on the safety of your data. Maybe they get attacked and all of their online backups get destroyed, and they don't have an offline copy.
When I look at Dropbox's backup policy they tell me what is backed up, but they don't tell me how. I just have to trust them. But I really know nothing about them.
1) Dropbox has many thousands of their own servers, alongside the Amazon. It's not like they're just using raw S3 and nothing else.
2) Dropbox has a history of egregious mistakes which they try to sweep under the rug. Only a very silly person would believe that Arash has suddenly decided to be open and honest with the customers.
Remember, when you talk about Dropbox, you're talking about a company that flat-out lied, claiming that they encrypted your data so they couldn't read it, and didn't stop lying until the FTC got involved.
So yeah... when somebody says Dropbox is better than X, I tend to think that person is deluding themselves.
What's the source on your third paragraph? I want to read the backstory there.
Edit: Bias alert; I work for Dropbox on our infrastructure team. I'm just curious about that particular incident, since it predates me and I'm always curious about these things.
Luckily for them (and unluckily for consumers) they got away with that particular lie during the early years where it was most valuable.
There's also a fundamental problem that Arash doesn't understand security. This was clear after the incident where no password was required in order to login.
Arash claimed that this was only a problem if you were one of the unlucky few who was actually hacked. He didn't understand that a risk exposure is also a serious problem, even if you happen to dodge the bullet on that particular incident. In fact, he seemed to get quite angry with paying customers who were upset by it because in his mind you don't have the right to be even slightly bothered by a major screw-up unless you were affected that time.
I understand that at this point Dropbox is huge, so it's full of people like you who don't have anything to do with the customer-hostile bullshit that the founders did... but it's still impossible to trust anything you guys do. After all, when the CTO is untrustworthy, only a very, very naive person would trust the product as a whole.
Personally, I use git-annex as my sync server, and all non-local transmissions are done over SSH using public key authentication, which is something that Dropbox will never implement.