The extra-pricing is very competitive, 25GB of extra space costs 2.49$ per month, 100GB are $4.99. For 1000GB (1TB) Google charges 50 dollars a month. Price drops at Dropbox should appear soon.
Remember: if you sign up to Dropbox with our Affiliate Link, you get 1GB of extra storage for free (a total of 3GB).
Dropbox Cloud Storage increases Free Accounts to 16GB (maximum), increased Referrals from 250MB to 500MB
Dropbox increased the maximum space for Free Users to 16GB: referrals were upped from 250MB to 500Mb per invited user, for "Pro" Account holders, the referral space was even upped to 1GB per accepted invitation. If you sign up to Dropbox with this link, you get an extra 500MB for your signup - that means you will start with initial 2.5GB free cloud storage. A maximum of 16GB is possible, if you invite some more people.
I mainly use Dropbox for Backups and Syncing my data between devices - the Dropbox application/client is available for almost all platforms. We can recommend using the free service as long as possible, since Google plans a new service that will be a strong competitor: the Google Drive Service (GDRIVE) could force Dropbox to lower prices drastically.
[Update 2012-03-11] with the Experimental Forum Build 1.3.21 the total of free space was reduced to 3GB and the import of 3gpp files was added.
I just confirmed this and got some 5GB of free permanent extra space on my dropbox account: using the Experimental Forum Build and being part of the beta test concerning the new foto/video upload feature. The beta client is available for mac, windows and linux.
The "Dropbox Camera Import" feature automatically uploads your photo and video content, when plugging in a SD-card or connecting your smartphone. The autostart of the Dropbox importer did actually not work when I tried on Linux and Mac OSX 10.4. On Windows, you'll need to have Autoplay enabled to get the automatic uploader working.
During this beta period, we are also offering additional free space to test automatic uploading of photos and videos. For every 500MB of photos and videos automatically uploaded, you'll receive another 500MB space bonus, up to 5GB total. The Dropbox space you earn is permanent. You can use it for the life of your account.
[Update 2012-2-22] the latest version of the Experimental Forum Build is 1.3.17 that fixes a lot of bugs and issues. I updated the links accordingly. If you are getting started with Dropbox, use this referral link to get 250MB of extra free space on signup.
First of all the bad news: currently there is no way to store any files directly in iCloud. That makes Apple iCloud not a competitor for Dropbox at all. But why do they state "you can access your content on all your devices" when they actually don't mean your MacBook or Macbook Pro? Well, they currently mean "all your iOS devices". While Apple could offer such a service (Backups from your Computer to iCloud) in the near future, currently it really doesn't make any sense to use iCloud if you are not using any iOS 5 Device - and if you also care about backing up other things besides your address book and photographs, let's say your 3D-models or local databases. In this context I can totally recommend iBackup, a free tool for OSX users that need point-and-click backups. In this case, you can backup right to FTP or your Dropbox, which gives you cloud-power as well.