The solution to this problem is a location based app which notifies the user of the close proximity of personal friends. The app gives the users control of how and when their location is shared with family and friends. Either user will have the option to remain anonymous when they are notified that a friend is near, giving them more personal control over their social interactions. This would eliminate the issue of unwanted encounters at inopportune moments.
To find out more about the application and its design process check out: http://blogs.computing.dcu.ie/wordpress/delanee9