Problem: People outside your project -- but who have the ear of the GoldOwners -- get hold of the iteration or release plan, causing your team to have trouble re-prioritising stories and making the developers feel bad for not implementing stories as fast as was originally projected.
Solution: make it clear that your estimates are just estimates and that things are going to change.
Solution: release very often. If someone was hoping for a feature to be released this week, they probably will barely notice if it comes out next week. But if your next release is a month away, they'll probably notice and start causing trouble.
Xp Planning Pitfalls