Do you have a Gmail Account. if yes than do you know all the Feature of Gmail. may be or may not be. Here i am going to tell you a Feature of Gamil. Each time when you send or reply or forward an email message to someone through Gmail, It automatically saves the email address of that person to your contacts list.
This auto- add feature is normally a good thing if you correspond with a limited set of person. But for everyone else, automatic contacts can quickly clutter your address book and it becomes ever more annoying if your contacts are set to automatically sync with your phone's book.
Now the Question is how to disable the auto- add feature in Gmail.
Just go to your Setting Page and choose "I'll add contacts myself" for the setting that reads "Create contacts for auto- complete" - now you'll have manually added email addresses to your Google Contact which am sure most won't mind.
Gmail Team has added few other enhancements like you get better warnings if you make typo in email address. More on the Gmail Blog.