I was supposed to head to 15 East for lunch today with a friend/colleague from a strategic venture fund.  We prearranged to meet around 12:30; but around 11:30am, I noticed my Twitter account freaking out when Fred Wilson posted that Union Square was closed off.

Since 15 East was right next to Union Square, I quickly emailed my friend and we arranged to meet down at Blue Ribbon Sushi in the West Village.  Had Fred not alerted Twitter, I would have never found out, and both my friend and myself probably would have been extremely late to the lunch since we were coming from two seperate areas of the city.  Twitter was finally useful.