1. Co-located data. Your data may be sharing a "cloud" with lulzsec who are trying to tear down the walls between users on your co-located server. Or worse, you could be sharing a server that will be confiscated by the FBI due to some data be deemed illegal.

2. Goolge does not focus on Enterprise. They have too many services and most of them are for consumers. They can't focus on any one of them long enough to give it all the attention it needs. Some services wither completely while others seem to be constantly evolving in to something else. What seems like a smart business decision today could be Google's next scrapped project.

3. Why buy a cow if you can get the milk for free? Play it safe, don't put all your eggs in one basket. Their free services are good for some things but you want to invest your money in more solid technology. -Insert farmer colloquialism here-

4. SaaS savings are a lie and a scam. What looks like a lower upfront cost will end up being a huge expense in the long run. The longer you stay on their service the less economical it is. Rates could change too. It is better to make an investment in your company than in theirs.

5. Loss of control. Once you move to the Google model it is a slippery slope in to chaos. Suddenly the IT dept. is cut from the budget and your employees want to bring in personal devices because they can access their Google apps from anywhere. Now you have no control over the integrity of the devices used to connect and not only is policy enforcement out the window but so is security. All it takes is one user with one botnet.

6. Chromebooks. The next step from Google apps is to deploy Chromebooks. They are new and untested. I don't believe any of the claims Google has made about them. You get what you pay for here.

7. Googles privacy policy. Seriously, go read it: http://www.google.com/apps/intl/en/privacy/
#1 on the list is "Use information to provide our users with valuable products and services." Does this mean that your Apps for Enterprise data goes in to their marketing database? Sounds like it to me.

8. You still need a separate web host for your corporate webpage. Hosting comes with e-mail for your domain name. Now you're not using gmail What else can we put on this "web host" thing? Calendars? Cloud storage? (from the FAQ) http://www.google.com/apps/intl/en/business/faq.html

9. Usage limit:
"Each account can currently send email to 2,000 external recipients per day to prevent abuse of our system and to help fight spam. If one of your mail accounts reaches the limit, the account will be temporarily unable to send mail."
If they get more traffic than they can handles they will inevitably have to throttle all of their users.