how do you recover your applications?You mean google apps? Well, you could keep a local copy of office around, it's not exactly rocket science.
When someone else hosts it, you're at their mercy.
And when you host it, you're at your own mercy.
Matching the availability of google tends to cost a little more than a hypothetical day of downtime would.
There are plenty valid concerns about hosting your office in the cloud. However, availability and TCO are normally the main arguments for google apps, not the other way round. Those infrastructure costs really add up when you're talking thousands of seats.