I made the switch from Google/NeuvaSync to Hotmail's native ActiveSync a few weeks ago. It work fine for a while but last week I began experiencing persistent sync failures that indicate "Communications error with server" or "server down for maintenance" or "Error in Exchange Server". If I deselect Contact syncing, the problem goes away.

In my hotmail account, I've 'imported' and/or 'linked' Contact stores from Facebook, LinkedIn, and Gmail. On the desktop, I'm sync'ing Outlook with Hotmail, and also installed the Outlook Social Connector for LinkedIn and Facebook.

I've not found a clear explanation for how these mechanisms inter-operate (or don't) so I'd love to learn what others think...