Spanning Sync consists of two components: the client that runs on your
Mac and a service that runs in our datacenter, which in turn talks to
Google. We chose this architecture for several reasons.

First and foremost it allows us to constantly improve the system--by
fixing bugs, adjusting to the frequent subtle changes in the Google
Calendar API, and adding new functionality--all on the server, without
forcing our users to install updates on their machines.

It also gives us the ability to spot and solve problems sometimes
before our users even notice there's something wrong.

Finally, it leaves open the possibility providing sync services between
online services. For instance, our next product will synchronize
calendars between Google and Salesforce.com.

We appreciate the privacy and security concerns of our users and take
steps to make sure that their private data stays private. We don't
store any calendar data; we only process it. Our background is in
providing similar services for our customers' most sensitive corporate
data (see http://spanningsalesforce.com), and we consider each user's
calendar data to be no less important.