In the 3 or so years I've used RefControl, I've added 5 exceptions. Sourceforge used to break (but not any more). NYT relies on the referrer to determine whethe

In the 3 or so years I've used RefControl, I've added 5 exceptions. Sourceforge used to break (but not any more). NYT relies on the referrer to determine whether you're allowed through the paywall. Some image hosts use the referrer to detect hotlinking (and subsequently block the image). I regularly use a webshop that uses a payment processor that relies on the referrer to do something (I'm not sure what). So it's fairly rare, but it happens, on occasion.