Okay, I tried to track down the originator of that article that fasteddie posted so that I could see where the statistics came from. The info in that article appears to come from the following report that was published in JAVMA (it's like JAMA, only it's for vets instead). It is now available on the cdc's website:
http://www.cdc.gov/ncipc/duip/dogbreeds.pdf.
In that article it states that in a study of dog bites conducted from May of 1975 to April 1980, 1 yorkshire terrier was involved in a DBRF (dog-bite resulting in a fatality). So basically, that info from fasteddies article comes from a report quoting another study that says 1 yorkshire terrier was involved in a DBRF between 1975 - 1980.
I am now trying to track down the original 1975 - 1980 study (The citation is Pinckney LE, Kennedy LA. Traumatic deaths from dogattacks in the United States. Pediatrics. 1982;69l:193–196 in case anyone wants to help
). Once that article is located, we should find more info on exactly how the fatal yorkie bite occurred. I'll keep you posted as soon as I find it.
Isn't it interesting how a statistic that there was one DBRF from a yorkshire terrier since 1975 has been turned into an analogy that yorkshire terriers are as vicious as pit bulls??