@kettch: Just thinking out loud... What about junk mail issues? Let's say my Windows Store App Mail account (corporate Exchange server) is whitelisted by the party(s) I'm sending the share notice to. If SkyDrive is sending it on my behalf it will look like it's coming from Outlook.com wouldn't it? While I like the removal of the dependency on desktop Outlook it looks like it can create another problem with the notice going to junk mail.
All-in-all the duality of W8 makes me cross-eyed sometimes. Maybe with Sinofsky gone there will be some flexibility here in the future.