For the ones that were affraid about the security vulnerabilities that Android has on Calendar and Contact Information, I have, actually Google has good news for them. This problem has been fixed in the version of Android 2.3.4 known as GingerBread.
Here is what Google says:
"Today [May 18th] we’re starting to roll out a fix which addresses a potential security flaw that could, under certain circumstances, allow a third party access to data available in calendar and contacts. This fix requires no action from users and will roll out globally over the next few days."
More details and security issues on: http://nakedsecurity.sophos.com/2011/05/19/google-rolls-out-silent-fix-for-android-security-vulnerability/