grep pipe filters broken on OSX Lion

generate_log

#!/bin/sh
# Script to generate logging output
while true; do
  echo $(date +%Y-%m-%dT%H-%M-%S) "WARN Here is a log message about events" 
  sleep 1;
done

gistfile1.sh

# Typically, this is since I'm tailing a log file and filtering out noise to get the lines that I'm interested in

$ ./generate_log > app.log&

$ tail -f app.log | grep events
2012-03-06T09-27-45 WARN Here is a log message about events
2012-03-06T09-27-46 WARN Here is a log message about events
2012-03-06T09-27-47 WARN Here is a log message about events
2012-03-06T09-27-48 WARN Here is a log message about events


$ tail -f app.log  | grep WARN
2012-03-06T09-27-07 WARN Here is a log message about events
2012-03-06T09-27-08 WARN Here is a log message about events
2012-03-06T09-27-09 WARN Here is a log message about events

$ tail -f app.log | grep WARN | grep events

# Nothing!