I've been reading a lot that having a specialty or a niche is very important. The idea is to be an expert or the top candidate in your field so you become the "go to" person. The last thing you should want is to be good at everything because then you aren't really good at any one thing.
My first job after college was working for a Chairman/CEO. And then I got laid off in a merger. However, even after the first CEO I was pegged as "the assistant to CEOs." So be warned - often unfairly, the first job you take out of college becomes your specialty.