Open Radar

 
Summary:
System Preferences > Displays allows you to configure where your mouse cursor goes from one display to the other. If you lightly drag your mouse cursor against the edge of the screen, this is respected. However, if you 'fling' your cursor really fast on the touch pad, OS X ignores the boundary set in system preferences

Steps to Reproduce:
1. Attach an external monitor to your computer (I'm using a Cinema display attached via thunderbolt)
2. Go to system preferences > Displays
3. Under the arrangement tab, set the external monitor to accessible only from the very bottom right of your regular display
4. Lightly drag your cursor against the edge of your display to verify that it won't go the external monitor under normal conditions
5. Finally, fling your cursor against the upper right of the screen to move it to the external monitor. (I used the built in touchpad of the macbook pro) Make sure to fling in an upwards and right direction, so that you know you won't 

Expected Results:
The cursor stays on the main display since it has not crossed the normal display boundaries set up in system preferences.

Actual Results:
The cursor moves to the external display

Version:
OS X 10.9 13A603

Notes:
Unfortunately I don't know how to record 2 screens at once, so I can only show in the videos that the cursor disappears onto the external monitor. However, you can see the cursor reappear at the bottom of the screen where I drag it back from the external monitor.