I found very interesting topic about ViewState.
This topic has been written in August 2006. Nevertheless it is very interesting and very comprehensive.
The guy's writing style is very attractive. Reading it, you like more and more the author's writing manner.
It's hard to stop reading it sometimes.
Highly recommended to everybody working with ASP.NET daily.
Follow here: http://weblogs.asp.net/infinitiesloop/archive/2006/08/03/Truly-Understanding-Viewstate.aspx