RTMPE Encryption might help. I'm not sure how GetFlv is dealing with live streams. Using Silverlight or HLS with Wowza DRM is one solution to your question since it is not flash based. Netflix does this.
The best you can do is use something like the upcoming Wowza Dynamic Overlays to mark the stream.
We already use RTMPE, I tried now using https but no luck. it still works
We also use a single token, a custom module that authenticate the view only once.. but somehow they changed and getflv is downloading the video as they come to the player.
If you are only using a view once link and they are still contuning to download the stream then I would suggest your view once code is not working correctly, and perhaps using HTTPS has not been done correctly.
If all techniques are implmented correctly blocking downloaders does work.