Facebook's terms of service came sharply into view this week after the social network website quietly altered the terms regarding data use. The changes made Facebook the controller of any work posted on their site - even if it was deleted by the owner. Facebook could use it in any shape, way or form and you wouldn't receive a penny. The resulting angry response of users prompted Facebook to change the terms back but i think this matter will rumble on for some time to come. Many people decided to vote with their feet and left Facebook because of this issue. I'm one of them.
Facebook is not a great place for artists. That's my final opinion after having a page for over a year. It's not that i hate Facebook. I just don't like the idea of any website subtly changing its rules at the risk of robbing me of potential income. Why should they have it? Copyright infringement is theft in the same way that someone walking into your house and taking your TV is theft too. It's just much more subtle. Check the website terms before uploading any material and even then, make sure that the work isn't high grade. Using the 'Save for web' function in Photoshop is just one way of controlling the quality of photographs you want the world to see.
So how do you avoid people 'borrowing' your online work? Well you can follow a number of steps to discourage potential thieves. If you have a blog i would limit the image size of photographs posted. The 35mm and digital images on my website are 551 x 365 pixels in size which, combined with the resolution settings, roughly works out to about the size of a 3x2 inch print. Large enough to get a good view on a computer monitor but not really good enough for a decent size print. Also put your copyright logo/mark on the images in a corner somewhere. A website/blog address or just a name and date will do and it'll act like an advert for your website in image searches.
I don't mind people who borrow images to promote me or if they link the websites. You have to be careful not too go too far down the protectionist road. Some photographers watermark their images so much that it spoils the photograph. Let people see the work and the talent you have but don't give them opportunity to take it and use it for their own ends. Protect your work. It's yours and yours alone.