Ajax Call from Telerik Report Viewer to pass requests to WebApi Service which is hosted in another server causes cross origin requests, AJAX in Web Applications uses the XmlHttp object which by default doesn't allow access to remote domains.
Enabling Cross-Origin Requests in ASP.NET Web API tries to solve the matter: http://www.asp.net/web-api/overview/security/enabling-cross-origin-requests-in-web-api#enable-cors