Was Facebook/Instagram Deal The Top?

I am not a computer geek, and probably just average in understanding what all the latest hot technology has to offer. So I have to say that yesterday's Instagram acquisition by Facebook puzzles me. I will not go into the fundamentals of the deal. Hold on, there are none to be discussed!!! 30 million people share photos on their mobile devices, with absolutely no current revenue or any plan thereof, it is free! I can not find any other reason for this acquisition beside taking out a competitor prior to Facebook's IPO. I guess Instagram was growing a bit faster than Facebook was comfortable with (my daughter did tell me "how cool Instagram is, and how she spends less time on FB now"). So in result, Facebook paid $1 billion for photo-sharing free iPhone app. (OMG, Apple, again...) If this was not the top of tech rally, then there must be one coming when Facebook goes public in May. Add another reason to "sell in May and go away". Or did Facebook/Instagram deal give us an early sell signal yesterday??