...when...
1) your sense of touch and hearing have improved as a result of feeling and listening for the blackberry vibrating in your belt or pocket
2) you know when you are about to receive a message due to the way the keyboard lags while in the middle of typing
3) everyone at works bypasses the IT department for Blackberry questions and go right to you
4) instead of asking someone to remind you or call you later about something...you tell them to "just send me an email"
5) you use your blackberry to get out of awkward social situations