We use Google Docs and GMail at DVFilm. Should we be concerned?  I  don't think so.  If I'm going to trust someone,  I feel Google is as trustworthy as anyone.  Here is one review of Google's term of service and another. We do not post proprietary information, passwords, or customer information.  The docs are internal docs that we use to document processes, take notes, and to help us stay organized.  The nice thing  about Google Docs is that it can  import AND export to various formats.  Export formats for documents include Word, HTML, RTF,  and even  PDF!  Spreadsheets can be exported as HTML, CSV, XLS and PDF.  Even if you kept your data locally behind a firewall, you shouldn't have just one location for important files.  So if you use Google Docs, backup!  That goes for email as well. 

I just setup Outlook 2007 to download all the mail from two Gmail accounts we use for support.  I created multiple mail profiles.  You can't do this within Outlook 2007, in Vista you go to the Control  Panel. In Control Panel mode, not classic, you select user Accounts, then Mail.  From here you can create  multiple profiles, not to be  confused with email  accounts which are where your mail  is stored.  I created two profiles and selected "Prompt for a profile to be used" which causes Outlook to prompt for a profile on startup.   I also created  separate data files.  Selecting Show Profiles, you select  a profile then select properties where you can create a new data file and make it the default for the profile.  You can  also manage the data files in Outlook by selecting File…Data File Management.