But ok, so they can see a video feed of my sleeping baby? So what?
It's amazing what you can gleam from little details. I would have thought that reading Sherlock Holmes would have taught many a geek that, even if we never learned how to do it ourselves. For a more recent piece of entertainment, see the now-ended series Monk or Psych.
Is there a window in the picture? Even if the shades or curtains are kept down, it could be used for information. For instance, if you have a tree outside that casts a shadow and it's windy a viewer can look up reported wind speeds in the Atlanta area and see if any particular area is stronger than others. If it's not windy they can watch the direction of shadows change over the day to find out what direction the window is facing. If it's night and they can see the typical flashing lights of emergency vehicles, they can check the various police blotters for the Atlanta area and see if any reported times match up with when they saw the lights.
If the curtains are pulled back maybe they can see a distinguishing landmark through them, even something as simple as a school or government building gives them a radius to work in. And if it's on the ground floor, facing the street, they can see other details about the area. Does it seem middle-class? Upper-class? Lower-class? Does your neighbor across the way have some super-gaudy lawn ornament? People have probably taken photos of it; take a screen-shot and do a reverse image lookup. Even if none of these say the exact address, they probably have an area name and maybe even a lat/long.
Does the monitor have sound? They could see if there's a nearby bell/siren that goes off at the same time every day. If you go in to pick up the baby while on the phone, they could overhear you reading your SSN or CC to someone over the phone (or, hey hey, your address.) Is there an ice cream truck sound? Probably a lot of kids and you're close to an elementary school.
Now, any one of these things alone are unlikely to identify you (except for you reading your address to someone on the phone), but together they can set up enough of a picture that someone in the area can drive around canvasing to nail it down. The camera itself can be used as confirmation; shine a non-obvious light or laser pointer (just don't hit an airplane) on a window you suspect to be the baby's room and have someone watch for it to appear on the webcam. The response to that, of course, is "Okay, so? Some guy knows where I live, so what?"
While the chances are extremely rare--more so than the fear-mongering media would like people to believe--there is a non-0 chance that someone will target you for whatever reason. Maybe they'll just send you creepy letters, or maybe you'll look at a recording of your baby's cam and see a face looking into the window at night. This doesn't mean you should board up your doors and windows, turn off the electricity, and never leave your house full of water and spam (questionably edible, not mail.) But why not take the time to activate security features offered on the camera already? Sure, that could be hacked, but security is about lowering risk, not removing it completely. Or, if it has no security features, unplug it when you're not home.
And, of course, we have the whole NSA thing going on, so why make it easier for them to collect stuff like this?
tl;dr: If you have the ability to enable extra security/privacy, likely trivially, why not?