The Jargon File (version 4.4.7, 29 Dec 2003):

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.