The information on the encryption is not that in-depth. While I also don't have more information than available on Web-site, from the information available it s

The information on the encryption is not that in-depth. While I also don't have more information than available on Web-site, from the information available it seems that they server-side encrypt all files with the same key which is (therefore) available to Dropbox. Maybe they just use an encrypted partition or something like this. If you want a similar system with better encryption look at Wuala or SpiderOak.