According to this article (http://blogs.msdn.com/junfeng/archive/2005/12/31/508423.aspx) and production issues encountered: using LocalDataStore is not a scalable approach for any web server that gets a significant amount of traffic.
The ThreadContext object should be modified to use [ThreadStatic] variables.
From the article:
The Whidbey RTM implementation of Thread.GetData/Thread.SetData has several scalability issues caused by global locks being taken. The appdomain-global lock taken in LocalDataStore.SetData is one of them. There is another global lock taken in ThreadNative::GetDomainLocalStore that is even worse since it is process-global.
The best workaround is to use [ThreadStatic] variables instead of Thread.GetData/Thread.SetData