Our (wrong) answer: Beef is always dead. Calling something "dead beef" is redundant -- a no-no for coders.
The actual answer, from a reader:
DEADBEEF is a hexadecimal value that has was used in debugging back in the mainframe/assembly days because it was easy to see when marking and finding specific memory in pages of hex dumps. Most computer science graduates have seen this at least in their assembly language classes in college and that's why they expect software engineers to know it. From wikipedia:
"0xDEADBEEF ("dead beef") is used by IBM RS/6000 systems, Mac OS on 32-bit PowerPC processors and the Commodore Amiga as a magic debug value. On Sun Microsystems' Solaris, it marks freed kernel memory. On OpenVMS running on Alpha processors, DEAD_BEEF can be seen by pressing CTRL-T."