In case you're curious, the lockup expiration will happen 180 days after IPO, or May 6, 2014. I already added a note to my calendar.
Are you expecting a similar drop as news articles go out about the pending lockup a week/days before, followed by it going up after some people realise everyone knew about this all along?
And, essentially, yes. Most lockup expirations, in my experience, seem cause a meaningful dip in the company's stock price. This happened with Zillow a couple years ago, it just happened to Tableau last week, and it happened twice to FB, and those are just the examples I can think of off the top of my head.
My guess is that the price drops because of so many employees selling at once, but I don't pretend to understand finance.