I work through a company that specializes in short sales, and they negotiate with the mortgage company/bank to pay fair commissions to realtors! They (16 of the largest lenders in the US) asked us at meeting what they (the banks, etc) could do to move more short sale properties, and we answered ; "Only two things are needed, fair commissions and speed in responding". It seems their biggest problem is agents that do not send in ALL the required documents, like proof of funds to close. Remember, short sale properties are sold "as is" and they will not accept a bunch of conditions - if the agent is on his toes, and knows how to package an offer, it is not unusual that we get a 1-2 day turnaround, when it used to take us 4-8 weeks!
The reason agents are requesting the buyers to pay part of the commission is because the banks/mortgage companies cut the commissions way down, and it takes so long to get to closing!