after the reserve fund broke the buck, the fed had to halt massive outflows of funds. it is not public where the funds were going, some if it certainly was justified concern about us money market fund safety, at the very least. Anyone watching matters should have been worried if they held a us money market fund.
Here’s a link to one of the discussions of this in 2009. The search term is electronic run.
http://www.freerepublic.com/focus/f-news/2329881/posts?page=101