Use this for people you are unsure about on your guest list.
Another way to cut down on guests is to eliminate kids. This may seem harsh, but you can always just limit it to college aged or high-school aged kids only. If all of your invitees have 2 or 3 kids, that adds up and can become quite costly.
Keep in mind that lowering your guest count is the best way to lower your out of pocket costs, less people = less tables = less rentals = less centerpieces = less meals = less overall costs to you.
Your wedding should consist of those closest to you that you want to share your life with. Not every joe shmoe you ever met!