There is a proper location.
There is a standard for proper filesystem structure. Its current version has been around for over a decade, which might be news to some Linux distros.
The latest version of the Filesystem Hierarchy Standard is 2.3:
http://www.pathname.com/fhs/pub/fhs-2.3.html
There, under the "Purpose" section of var, it explains why that's a bad idea to use /var/backups:
Several directories are `reserved' in the sense that they must not be used arbitrarily by some new application, since they would conflict with historical and/or local practice. They are:
/var/backups
/var/cron
/var/msgs
/var/preserve
The proper place would be, dependent on the application and its usage, something like:
/var/lib/<app>/backups
/var/local/<app>/backups
/var/opt/<app>/backups
(I say "something like" because whether you use /var/lib, /var/local, or /var/opt is dependent on the application, its role within the system, and how it was installed. Also, the structure under /var/lib/<app> is arbitrary based on the application maintainers.)
By the way, since you mentioned it, /var/www is not the proper place for served web pages (again, this is news to some distro and package maintainers, but the FHS is older that many of them who clearly never have read it). Served content, and stored application data/assets for services belong under the /srv directory. I have been using the protocol method since 2005 and find it works quite well (/srv/http, /srv/ftp, /srv/git, /srv/svn, etc.).
Let's say that that you are using rsync and that this machine is providing a backup service for the network, you would use:
/srv/rsync/backups
UPDATE
Version 3.0 of FHS:
https://refspecs.linuxfoundation.org/FHS_3.0/fhs/index.html
Best Answer
The following is a list of the cloud services similar to Ubuntu One that work in Ubuntu (Can be installed with a .DEB file) and may provide support for the Unity Systray:
Dropbox
Website - https://www.dropbox.com/
Starting Free Space - 2 GB
Bonus Space - 25 GB to 50 GB when used on an Smartphone
Characteristics - Sync Files/Folders between devices.
Unity SysTray Support- YES
Open Source - NO
InSync
Website - https://www.insynchq.com/
Characteristics - Sync Files/Folders with Google Drive. Extensive Sharing properties. 15 Day Trial.
Unity SysTray Support - YES
Open Source - NO
OwnCloud
Website - http://owncloud.org/
Characteristics - Sync Files/Folders between Devices on your "Own Cloud".
Support - http://owncloud.org/providers/
Unity SysTray Support - YES
Open Source - YES (GitHub)
SpiderOak
Website - https://spideroak.com/
Starting Free Space - 2 GB
Characteristics - Sync Files/Folders between devices. Advanced GUI System & File History
Unity SysTray Support - YES
Open Source - NO
Wuala
Website - http://www.wuala.com/
Starting Free Space - 0 GB Paid Only
Characteristics - Sync Files/Folders. GUI System and an easy way to manage files across devices.
Unity SysTray Support - YES
Open Source - NO
Tonido
Website - http://www.tonido.com/
Starting Free Space - 2 GB
Characteristics - Sync Files/Folders between computers.
Unity SysTray Support - YES
Open Source - NO
TeamDrive
Website - http://www.teamdrive.com/
Starting Free Space - 2 GB
Characteristics - Sync Files/Folders between computers. File Collaboration (Multi User Support)
Bonus Space - Up to 10 GB by inviting others.
Unity SysTray Support - YES
Open Source - NO
SeaFile
Website - http://seafile.com/en/home/
Starting Free Space - 1 GB
Characteristics - Sync Files/Folders between computers.
Unity SysTray Support - YES
Open Source - YES (GitHub)
Syncany
Website - http://www.syncany.org/
Starting Free Space - Depends on which cloud service you use
Characteristics - Sync Files/Folders between computers. Can use Picasa, RackSpace, Amazon, Google, Windows Share and even WebDAV as a repository. Nautilus integration. Advanced GUI. Can integrate with other Cloud Services. Very flexible.
Unity SysTray Support - YES
Open Source - YES (GitHub)
Copy (Barracuda)
Website - https://www.copy.com/home/
Starting Free Space - 15 GB
Characteristics - Up to 5 Devices Synced, 5 GB+ for every invite, Can personalized space provided for a single user. Nautilus integration. Advanced GUI. Can integrate with other Cloud Services. Very flexible. Supports soft symlinks.
Unity SysTray Support - YES
Open Source - NO
Others that may be used (Open Source):
Others that may be used (Closed Source):
In my case I stick with Dropbox and InSync. Tried SpiderOak and there was a lack of User-Friendliness that I did not use it after a week. InSync is pretty cool (Saves me a lot of time). Lastly Syncany has pretty cool options to connect to other cloud services and even create your own for privacy.