I couldn't find a TSB (technical service bulletin) for this problem. It may be that they replaced it because your vehicle was still under warranty.
I can't seem to find anything that says this is a common problem.
〉 Answered on Jul 18th, 2008 by Lori Johnson, Owner and Instructor at Ladies Start Your Engines
I have not heard of any news about this. If you would like more information as to what the problem was, I'm sure Toyota has literature that will go in depth for you.
〉 Answered on Jul 18th, 2008 by Suzanne Grego, Technician at City of Philadelphia Fleet Management