Just got an email from Matthias Meißer, who is one of the sysadmins on OpenStreetmap that my COSMCtrl control appears high up in the list of User Agent strings which hit the OpenStreetmap slippy tile server. He informed me that they employ various techniques which are based on the User Agent string of client applications to control their bandwidth requirements. If you are considering integrating COSMCtrl into your client app, then please ensure that you use your own unique string for your applications User Agent string so that it will not be blocked because of some one else abusing the same string. To change the User Agent string you can use the COSMCtrl::SetUserAgent method. The default value will be taken from the MFC application using the global method AfxGetAppName().