How about this one that bizhat uses and recommends in the wiki? http://docs.buyscripts.in/Vshare_flv_hotlink_protection

Code:
RewriteEngine On
RewriteCond %{HTTP_REFERER} !^$
RewriteCond %{HTTP_REFERER} !^http://(www\.)?yoursite.com(/)?.*$ [NC]
RewriteRule .*.(jpg|flv)$ - [NC,F]
From htaccess tools:

Some surfers uses a personal firewall or antivirus program, that deletes the page referer information sent by the web browser. Hotlink protection is based on this information. So if you choose not to allow blank referers, you will block these surfers. You will also prevent people from directly accessing an image by typing in the URL in their browser.
With this in mind, why would you want to disallow blank referrers? Unless it's to prevent people from directly accessing an image (or video) by directly typing in the URL in their browser (and thus downloading it).

If that is the case, one measure you can take is to add a subtitle to uploaded videos so that no matter what, the URL of your site will be on the video. Search the forums for "hardcoded watermark" or something along those lines or check my site webgeek-design.com and look in the FREEBIES section.