For one reason, Google has a paid enterprise offering that they sell under contract and dropping support for this is the second shoe to drop in breaking one of its most important components for commercial use. Not every small business has the resources or inclination to DIY their own hosted calendar service, especially when they're already paying for one.

There's Baikal Server[1], which is a pretty neat project that allows you to host and manage several CalDAV and CardDAV accounts on a server. Have been running it for nearly two months with absolutely no issue.

Nobody's pulling the rug out from under me. Except me.

[1]: http://baikal-server.com/

For me, I have no problem running my own contacts/calendar server with calDAV/cardDAV support. I really hate running email servers though - and it's really nice to have your contacts and calendars integrated with your webmail.

I've been looking for a good calendar/contacts server, my general requirement being a really understandable backend data format (i.e. so I can just copy my home directory off the server and get everything).

Radicale looks nice, but I haven't managed to get it to work properly so far.