When making a guest list, you should plan for 100% attendance, never counting on certain people to RSVP "no" because of x or y or z. I've seen this warning on here all the time, and I've always thought to myself, "that makes sense, it's common wedding-planning knowledge, right?" Wrong.
A friend of mine has set a budget for 150 guests, saying that was the highest number of guests they could afford to accommodate, and how they were hoping for closer to 100-120. I've been thinking throughout her planning that 30-50 declines would be a lot, but kept my mouth shut because she is an adult who is capable of making her own decisions, or so I thought. She is two weeks from her wedding and had a breakdown this week, telling me that out of the 215 they invited, 198 are attending. That's right, she planned, bugeted, and made contracts for 150 people, after sending out 215 invites! I have NO idea why she thought she would get nearly a 50% decline rate, but she was very, very wrong, and is now in a very tight situation financially.
Don't do it! Save yourself! Plan for 100%!!