If you're looking for a job, read this: BusinessWeek's Twelve Job Interview Mistakes.
This one is #6. Arriving Too Early
Everyone knows the downside of getting to an interview late, but arriving more than 10 or 15 minutes before the start of a meeting is just as unacceptable. “It makes the company uncomfortable because they are customer service-oriented. We can't do anything if they see somebody sitting there for 45 minutes because we do so much interviewing that we usually have to stick with the schedule,” says Susan R. Summers, vice-president of human resources for Episcopal Ministries to the Aging, which has care facilities in the Mid-Atlantic. Summers' advice if you get there too early? “Stay out in your car or sit on the bus bench and wait.”
Thankfully, I'm one of those perennially late people.