How did imessage start executing on my phone?

Question

I was trying to make a one-one appointment with the apple store, because their website has been troublesome for the past
week or so.   After we made the appointment (which took over an hour and I was on hold 5x), while I was still on the phone with
Apple store, I got a dialogue box on the phone that distracted me because it popped up on top of what I was doing, it
flashed my yahoo mail account as the id on the phone and asking for my password and it knew my yahoo mail account. 
Did something or someone automatically sign me up for iMessage?  Who told it to use my email?  Its an application I did not install.
A similar problem occured with Apple mail.  I never use Apple mail and it automatically fired up and tried to log in to my yahoo mail account.
How do we control this stuff?  I no longer even know what is running on my machine or how to stop it.  How would I determine
if private data has been sent somewhere?  I certainly did not give apple mail my permission to use my yahoo mail account, etc.
What's up?   

Answer 1

Hi,
Lion (OS X 10.7.x) draws info from your Keychain.
In places this info in System Preferences > Mail, Contact and Calendars.
It will presume you use any email IDs in Mail.
As Mail can create NOTES these may also be activated in the Mail, Contacts and Calendars pane.
In some cases some Apple IDs ending in @mac.com and @me.com are also valid in iChat or the Messages Beta if you have it installed.
As Google and Yahoo names can be used in iChat/Messages these may also have been "turned On" in the Mail, Contacts and Calendars Pane.
Emails accounts can be turned Off in the Mail, Contacts and Calendars Pane or disabled in the Mail App.
If your Apple ID is linked to iCloud then you may need to look at the iCloud pane as well in System Preferences.
If you have Messages beta installed and entered an Apple ID to make it work it will use this to Sync with your iPhone.
The info about this is "sort of" there on this page
Nearer the bottom is the bit on System Preferences
Set up online accounts
The new Mail, Contacts and Calendars pane in System Preferences gives you a central location to set up and manage all your accounts, including Microsoft Exchange, Gmail, Yahoo! and AOL.
What is does not say is that it is ON by default.
It may be more that you did not Deny the OS to do these things rather than something that you had to allow it to do.
9:00 PM      Sunday; July 8, 2012
Please, if posting Logs, do not post any Log info after the line "Binary Images for iChat"
  iMac 2.5Ghz 5i 2011 (Lion 10.7.2)
 G4/1GhzDual MDD (Leopard 10.5.8)
 MacBookPro 2Gb (Snow Leopard 10.6.8)
 Mac OS X (10.6.8),
"Limit the Logs to the Bits above Binary Images."  No, Seriously