Some of the worst advice I've ever heard given to new freelancers is to pick one subject you're interested in and stick with it. No editor is going to hire you if you've been published on several different topics. This doesn't seem right. Certainly, if you're incapable of crafting a pitch that effectively convinces your editor that you're qualified to discuss a topic, then that's a problem. But no editor is going to say, "This is a great pitch, but I see that you have also written about a differen subject for Salon, so forget it."

However, there is something to be said about finding your focus so that once you have established yourself, you can find a specialty and become an expert. Absolute Write published an article from the American Writers & Artists Institute about how to specialize, without feeling trapped with one topic.