I personally don't think so, but I understand why it happened. New tax appraisals occur every 3 years. It's impossible for all of the reappraisals to be done in one year, so many of the appraisals were done in 2006 and 2007, times when prices were still higher.
There has been much of an outcry because of this. Another factor that has caused a lot of controversy is the fact that the Benton County assessor has not adjusted the value of other homes in a given neighborhood when the value of a similar home has proven to be lower (i.e. sold recently for less). The Washington County assessor has stated that this kind of adjustment IS occurring in Washington County.
For more specific information about the situation, I would suggest that you read my blog, whose web address is listed below. There are several entries on this situation in the past few months.