As PhonicUK said: if your browser shows something, a user will always have the possibility to store that information somewhere. You'll never be safe, unless you implement some kind of encryption, but you wouldn't want to do this yourself. If you offer the video files for download, even worse. When a client has a file to store on their computer, it's completely up to them what they want to do with it. They can copy it to other devices, upload it online, etc.
And this is not a bad thing. Whenever you try making it harder to rip a video, you make it harder for regular paying customers to get and use the content as well. This is, in essence, annoying. Several companies have tried to enforce copyright schemes upon users and majorly screwed it up. For example, there was a time where CDs were only playable on a computer by launching a separate clunky piece of
software rootkit. Needless to say no honest paying customer liked that. Music distribution services like iTunes used to sell DRM-protected files, but later decided to ditch that.
Making your customers happier could make them recommend your services, and not shoving a complicated and customized copyright protection (like supplying the files in an application that decrypts them) will make you stand out as the good guy. So far, almost every protection was broken at some point anyway. Your business really should not rely on the content alone, but on the satisfaction of the customers primarily.
Now, for businesses that depend on monetization of their content, and where piracy would cause major loss (if there's a way to measure that is debatable), there are streaming services that specialize on content distribution with proper access right management and content protection. Brightcove is one of those services:
Protect your valuable contentEnsure your video is safe. Use RTMPe stream encryption and SWF verification to prevent video stream ripping and content theft and ensure that your video stream plays back only in your authorized players.
There are similar services, who mostly partner with broadcasting institutions (TV channels, etc.), but note that if you decide to go that route, you will have to pay for the service. These services don't work miracles though. If you can view something on your computer you can easily run a desktop recording software and capture it to a file. If the file's been viewed in the browser it was cached somewhere as well. So, in essence, expect your customers to play nice, and play it nice yourself.