This guy explains it better than I can, but the meat of it is that a large number of Intel Ethernet controllers in the field are susceptible to a firmware bug that can shut down the Ethernet port remotely.
http://blog.krisk.org/2013/02/packets-of-death.html
Wow. Just, wow.
Meanwhile, Broadcom controllers have their own persistent bugs. Whose Ethernet chipsets can you rely on now?!?
-Adam Thompson