I've been using MS Live Mesh for online storage and synchronisation for a while now. Specifically, the killer app for me has been the ability to share files with mates; I've had a folder on my desktop with a mate's name, drop files into it and it appears on their desktop automagically. Unfortunately, MS in their wisdom have dropped support for XP when they moved Mesh out of beta, rendering it useless.

So, does anyone have any recommendations for an online storage provider that supports sharing between accounts and doesn't encourage spamming everyone you've never met with referral links every five minutes? Ie, not bloody Dropbox?