Typing the following into the Windows version of UCBLogo 6.0:
to factorial :n
output ifelse (:n=0)  [:n*factorial :n-1]
print factorial 10000
print factorial 100000
results in UCBLogo going into a (Not Responding) state according to Windows Task Manager.
It seems like the students in my class cause UCBLogo to freeze in a similar way while they're experimenting.