Sometimes being a microbiologist sucks....
Hot Dogs as well as other cold lunch meats can contain Listeria. While this isn't so much dangerous for bros like you and me, it can cause complications to certain people (especially pregnant women). One time when I was working in the lab, I got yelled at by the boss's boss's boss for bring back a Subway sandwich that a pregnant girl had asked for.
Quoth the CDC:
"Recommendations for persons at higher risk, such as pregnant women, persons with weakened immune systems, and older adults in addition to the recommendations listed above, include:
Meats
Do not eat hot dogs, luncheon meats, cold cuts, other deli meats (e.g., bologna), or fermented or dry sausages unless they are heated to an internal temperature of 165?F or until steaming hot just before serving."
CDC - Prevention - Listeriosis
I have also been told that just microwaving a hot dog is not good enough because the microwave cooks from the inside out. Even though the internal temperature of the dog may be adequate to kill the pathogen some may remain on the surface which has not reached the lethal temperature.