Aero Shake is a new feature that was introduced in Windows 7 for managing windows. What it basically does is minimize open windows when one active window is selected and shaken back and forth.
In case this feature is not needed, it can be disabled. Here is how to do it in Windows 8 (this works in Windows 7 as well) :
Go to Start > Run and type “gpedit.msc”
This will launch the Local Group Policy Editor. Drill down to User Configuration > Administrative Templates > Desktop.
From the right side of the pane, double click on “Turn off Aero Shake window minimizing mouse gesture”.
Change the settings from “Not configured” to “Enabled”. Hit Apply for the changes to take place.