One challange making things extremely difficult to overcome can be Mortgage Insurance on a second.
Good luck with the article,
Anyway, short sales have many possible issues one of the main things is the agent needs to be dilligent in communicating with the banks, faxing and re-faxing information over and over again, banks losing paperwork, requiring updated paperwork after they dilly dally for long periods during the period a negotiator is waiting to be assigned, is assigned and then takes their time in the negotiations.
Agents dealing with short sales need to be patient and be prepared to make many phone calls and repeat faxing. Advice, scan all your documents and fax the docs from your pc, it will keep you better organized and makes it easier to re-fax instead of standing in front of the fax machine for hours on end. Guess I'm giving more advise opposed to listing things I have in dealing with short sales but then again your question was way too vague, guess your writing a book or trying to put together a course of some sort, I would disclose that in your question if that is your intention.