Cell phones carry a lot of information. The new breed of smart phones have our whole life's information in one place (calendar, contacts, social media sites, banks, mail, shopping, etc). Having our cell phone stolen or lost is a known hazard. Another hazard is someone stealing the information off your phone as you pass by.
It seems that some phones have automatic access and don't have to ask permission - the purpose is to tell you when you've missed a call or received a text message.
Read more at:
http://news.menshealth.com/your-phones-biggest-security-risk/2011/12/07/?cm_mmc=Twitter-_-MensHealth-_-Content-MHNews-_-PhoneSecurity
Bottom line:
1. Close opened apps not in use
2. Encrypt sensitive data
3. Lock your phone
ex: The Perfect App Protector (android), Pic Lock (iphone)
4. Install antivirus
5. Beware of email scams asking you to click unknown links
6. Install a phone tracker
ex: Mobile Defense or Find My Phone
Gotya Face Trap takes a picture if the screen lock password is incorrect and emails it to you along with the phone's location