I just came across this great article on Jugglezine filled with interesting email overload facts:
"In 2006, the average corporate e-mail user received 126 e-mail messages
per day, a 55 percent increase since 2003, according to a survey
by The Radicati Group, Inc., a technology market research firm in Palo
Alto, California. "If users spend an average of one minute to read and
respond to each message, this flood of e-mail traffic will consume more
than a quarter of the typical eight-hour workday–with no guarantee
that users actually read the messages that are most important," the
report said. "Additionally, if e-mail traffic continues to increase at
this rate, the average corporate e-mail user will spend 41 percent of
the workday managing e-mail messages in 2009."
The article also has a wealth of tips for "seizing control of email." Check it out.