Search Web Service and Account Permissions

Created a simple desktop app to query SharePoint and return data.

Web Reference: http://webApp/managedPath/siteCollection/_vti_bin/search.asmx

Site structure looks like this:
http://webApp/managedPath/siteCollection

Place a user account in the site collection and give it read access.  

Execute a search from the desktop app and receive the follow error: {System.Web.Services.Protocols.SoapException: Server was unable to process request. ---> Attempted to perform an unauthorized operation.

queryService.Credentials = new System.Net.NetworkCredential(@"testAccount", "password", "domain"); 
                System.Data.DataSet queryResults = queryService.QueryEx(GetXMLString());

The search only works if I give the user account read access to the root web app. 

Is this by design or am I missing something?

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