http://visual.ly/track.php?q=http://visual.ly/history-and-influence-hashtag?utm_campaign=website&utm_source=sendgrid.com&utm_medium=email&slug=history-and-influence-hashtag?utm_campaign=website&utm_source=sendgrid.com&utm_medium=email
by mainstreethost.
I rather doubt that 1988 was the first point when hashtags were used to tag content. I was using them with a customer relationship management system in the mid-90s and I had the impression then that this was something that went back a long way in that kind of computing, back to the days before personal computing.