Generally custom web applications that interact with K2 impersonate the current user for security by setting this attribute in the web.config file:

  <identity impersonate="true"/>

But sometimes you want to perform some code in the security context of the account that runs the application pool.  There is a simple way to do this in code:

using (System.Web.Hosting.HostingEnvironment.Impersonate())
{
           //Code in here will execute as the application pool identity instead of the current user

}

I knew it could be done, but it took me a couple of hours of searching to find it.  Here is a great article with some ideas on the subject: 

http://httpcode.com/blogs/PermaLink,guid,961b0893-cebf-47e2-a608-9562136bcad4.aspx