When a person puts a shift into the marketplace, they should be able to declare the shift an 'emergency', that will send the shift to all users immediately. A few considerations:
There should be a penalty for these blasts to prevent abuse. For now, perhaps allowing the posting of only 2 or 3 blasts per month.
Users should be allowed to turn off these blasts and NOT receive them. However, if they do not receive these blasts, then they should not be allowed to send them.
To prevent abuse of (2), if users change the setting, they should be unable to change it for about a month to prevent rapid cycling.
When a person puts a shift into the marketplace, they should be able to declare the shift an 'emergency', that will send the shift to all users immediately. A few considerations: