Short sales are hard to work with for many reasons, the first being the situation itself. The person facing the short sale is very unhappy. Couple that with the bank looking over their shoulder at every turn and the constant barrage of phone calls from folks off the street asking to purchase their home at half price. That is just from the homeowners perspective.
From the agent's perspective, 9 times out of 10 you have no idea the home is a short sale (depending on your local MLS) so you believe you are working a regular offer only to discover too late, whoops a short sale. Or better, you have a buyer who is only looking for short sales and they know from several sites that there are "hundreds" of foreclosures in your town and gives you the list. As you troll around to discover if the home is listed, what point of the process is the home at and whether a lender is involved, you talk to irate home owners, exhausted and frustrated listing agents and overworked lender property minders.
Then you make a low ball offer and are rejected for the very simple reason of the definition of a short sale - the owner owes more. The current owner can not accept a low ball offer because they don't have money, not a surprise considering they are in foreclosure. The bank doesn't want to lose half of it's investment and often times can't. (Some lending institutions are beginning to move inventory now.)
To answer your initial question, the answer is a few. We are all being invited to take classes on short-sales, usually from the listing agent perspective. There are many horror stories from buyer agents, of lending institutions cutting an agents wages by 2/3 after the offer has been accepted. Could you imagine being asked by your employer to do three times the work for 1/3 the salary?
So, if you don't find agents jumping all over themselves to guide you through the short sale buying process, please don't be surprised or angry. It is just an ugly and sad process for everyone involved.