As you are aware HTC has partnered with Dropbox for cloud storage, and now Sony Ericsson has joined Box.net and the company is offering storage service to Xperia owners in UK. Box.net has partnered with Sony Ericsson and is offering 50GB of free cloud space for every Xperia smartphone owner in UK.
To activate the offer, just download the Box.net application from the Android Market and create an account on Box.net if you don't have one already. Once you login from your handset you get the free storage. But as far as the sources say, the free service offer is only valid if you open an account before 31st December 2011.
The service is exactly the same as offered by Dropbox, so don't be surprised. The only advantage is the huge 50GB of storage. You can store and share your content and is also secured as Box.net uses SSL encryption, redundant storage, configurable permissions, and more.
Source : Mobigyaan