Originally Posted by Nautilus

Streams could be either progressive DRM protected and tied down to your server's MAC address, or encrypted and RMPT - those are really hard to break except for screen recording which 98% of the file sharing crowd would not bother with.

You can also fly their IPs and logins above the video to additionally scare them from sharing your videos, and on top of it add an invisible watermark that cannot be removed with whatever info you want (IP, login, date etc) - and you're close to keeping 100% of your stuff inside of your member area.

Even if content protection technologies were less effective, you're still strongly advised to use them - even 50% less of file sharing is a small victory. But technologies available today are close to being 100% effective, not to use them is simply foolish.