My inspirational quote for my diary today was "This is not a pen, it is a prayer" Sadly it is unattributed. Even documents devoted to writing seem to have trouble with proper attributions.
The actual quote is, "This is not a pen, it is a prayer, one must have compassion for that.” - Fyodor Dostoyevsky
It seems to me that now more than ever we are living in an age when knowing where something comes from, and to whom it belongs is irrelevant. As someone who has large pieces of my creative output digitized on the internet I can say honestly, it's not irrelevant.
If you are an artist you need to mark your photos with your name or website so even if people steal your picture without credit your name is still on there. This is important for so many reasons, not the least of which is copyright, and clearly if you are an artist trying to make a living having your art tagged with a way to find you can give you sales. And I don't know many artists who couldn't make a few more sales.
If you have the urge to share something that you like, don't be a dick, make sure that you link back to the site where you found it so they can get some hard earned traffic. This isn't just for pictures and art, but for everything that you want to share including quotes (which are also subject to copyright). Just add a link or a name so you aren't denying someone their livelihood. Making something "go viral" is only awesome if the person who created it gets the credit for their brilliance.