McQuary limit
[from the name of the founder of alt.fan.warlord
; see warlording.]
4 lines of at most 80 characters each, sometimes still cited on Usenet as the maximum acceptable size of a sig block.
Before the great bandwidth explosion of the early 1990s, long sigs actually cost people running Usenet servers significant amounts of money.
Nowadays social pressure against long sigs is intended to avoid waste of human attention rather than machine bandwidth.
Accordingly, the McQuary limit should be considered a rule of thumb rather than a hard limit; it's best to avoid sigs that are large, repetitive, and distracting.
See also warlording.