I really like Dropbox. I also liked the old gDrive a lot. Now that computers are using SSDs, and so far the cost for big SSDs are still high (at least for countries outside US, like Brazil), is there any way to use Dropbox like the old gDrive? I will try to explain what I want:

With Dropbox, a folder is created on your PC/MAC and every file inside this folder will be synchronized with Dropbox. But the problem in this scenario is that a file is still consuming space in your hard drive. The old gDrive used to create a Drive in your PC/MAC, and every file inside it was not in your hard drive. For me, gDrive was like a network shared folder, and it allowed me to have files that look like they were in my hard drive but they were not.

I know that I can tell Dropbox to no sync certain files or folder, but I want to use it completely online so no file will be on my hard drive (despite the fact that it looks like it is).

You can use Expandrive for storing your files on a server that would sync your files to dropbox. It’s not free, you can try it for 7 days, and after that upgrade pricing is $19.95.

From the website:

Seamless Access to Cloud Storage

SFTP/FTP, WebDAV, S3, OpenStack Swift, Dropbox, Google Drive and more.
Just like a USB Drive, in any application.

Cloud storage in every application

ExpanDrive acts just like a USB drive plugged into your computer. Open, edit, and save files to remote computers from within your favorite programs—even when they are on a server half a world away. ExpanDrive enhances every single application on your computer by transparently connecting it to remote data.

Finder & Explorer is your user interface

With ExpanDrive, you can securely access any remote file server directly from Finder and Explorer, or even the terminal. No need to open a separate transfer client just for file transfer. ExpanDrive extends the way all applications can access data.

Available for Mac & Windows. : Linux version coming mid-2014

Expandrive Screenshot : Windows

Expandrive Dropbox Screenshot : Online via Browser

If this option is not valid, then I’d suggest you read THIS PAGE on dropbox, where this question has been asked. My answer to your question is based on a comment from this page as well. Apart from this answer, most of the posts are requesting the same feature for dropbox. According to the few answers, dropbox doesn’t support this, but you can get this done via the Expandrive.

Dropbox probably is not good for this. On the other hand OwnCloud (http://owncloud.org/) is perfect for this. You can mount your files with WebDav (native support on Gnome/KDE/Windows/Os X). You can host it yourself or find free/cheap providers.

I’m 99% sure this can’t be done using plain Dropbox. You might find some extension to Dropbox that would do that, but it would be so complex to the point where it won’t even make sense to use Dropbox for it anymore.

I don’t think Dropbox is designed to work this way, but you can upload files to dropbox rather than sync them.

Log into the site, then choose the option to upload files. You should probably put them all in a folder that you will not sync.

So the files will be on Dropbox, but not on your computers. You can access them anytime through a web browser.

I know this is not exactly an answer to your question, but I think it is the closest Dropbox can get to doing what you want.