Because MyDisk.se doesnot work with Vista 64 bit I prefer SpiderOak
SpiderOak Bonus-Registration-Link:
Starts with 3GB instead of 2GB, max. reachable 2 + 3x1GB = 5GB:
https://spideroak.com/download/referral/11ae56d2017b64ccb8b010aa0131d99a
http://fwd4.me/FBP
2 Advantages of SpiderOak in comparison with DropBox:
(A) With the Bonus-Registration Link you start SiderOak with 3GB instead of only 2GB (DropBox)
(B) In DropBox you can only synchronize one directory with sub-directories
With SpiderOak you can Synchronize as many different local directories as you want
(B) In DropBox you can only synchronize one directory with sub-directories
With SpiderOak you can Synchronize as many different local directories as you want

I can't say enough good things about this service. If you are looking for cheap webDAV storage and access, especially for an alternative to having to suck up the Apple Tax and cave to MobileMe, this is an excellent choice. While the service does come with a back up application, I have yet to use it because I have a different back up scheme that works just fine for me. It is also not designed to be sync service... if anything the focus is on completely on its webDAV functionality and the inherent features of that protocol - primarily the ease in provides with document sharing. Their privacy policy is short and a bit TOO concise because it leaves the average person wondering, that's it? Oh I dunno about this. But as a European company, I feel the fact they are subject to stricter privacy guidelines than a company based in the U.S. makes me comfortable with using them and feeling my data is safe. It's been almost 2 years now and I haven't had any problems with data loss or corruption. I did notice for a time that the service would be unavailable at like 2 or 3A, Pacific Time, presumably for maintenance, which would be sometime during the day in Europe so that left me a little puzzled.