My wife doesn't like walking the dog when it gets late and I can understand that it can get worrying late at night. You never know who you'll meet. Imagine that a stalker uses this location-based information to get to you. Let's say that it's not a stalker, but someone you just don't want to see, like an acquaintance or something like that. Even if it's not dangerous, it could become annoying.
2. More Crime
While I'm not worried about my friends coming to my home and fleecing me, I'm more concerned who exactly gets to know where I am. I distrust Big Brother, and wouldn't like to let anyone know where I always am, especially Facebook. This type of information can be used to burglar your home when you are away. This could be done by a friend of a friend, or some remote connection like that.
3. Unintentional Lies
There aren't many people who can say that they skipped out of work to have fun. The difference is that with Facebook Places, your employer, boss, or colleagues can be made aware of where you are and what you are doing. Let's say that you are taking a sick day to go to a concert, and then let your friends know inadvertently where you are. This can easily trickle back to your employer and colleagues, if they are part or attached to your social network.
4. Checking Other People In
You can check in your friends as being in the same location. Is this a bug or something that's a problem? It could be problematic, but you can easily un-tag yourself by editing your news feed. However, will everyone do this?
5. Changing Places' Names
Once a place has been entered in Facebook Places, it's unclear how you can change the name of it. Say for example, that as a joke, your home was entered as 'rehab center' or 'roach motel'. For now, it seems like it's not possible to change this.