Think about the pictures of a horde of tourists assembled in front of the Mona Lisa, their cameras clicking away. It is the most photographed work of art in human history. You can see it in full light, low light, close-up, far away, x-rayed; you can find parodies of parodies of parodies; and yet, seeing it in person and walking away does not suffice. The experience must be captured, the painting itself possessed, a poor facsimile of it acquired so that you can call it your own – a photograph which, in the end, says, I was here. I went to Paris and saw the Mona Lisa. The photo shows that you could afford the trip, that you are cultured, and offers an entrée to your story about the other tourists you had to elbow your way through, the security guard who tried to flirt with you, the incredible pastry you had afterwards, the realisation that the painting really is not much to look at and that you have always preferred Rembrandt. The grainy, slightly askew photo signifies all these things. Most important, it is yours. You took it. It got 12 likes.
This is also the unspoken thought process behind every reblog or retweet, every time you pin something that has already been pinned hundreds of times. You need it for yourself. Placing it on your blog or in your Twitter stream acts as a form of identification – a signal of your aesthetics, a reflection of your background, an avatar of your desires. It must be held, however provisionally and insubstantially, in your hand, and so by reposting it, you claim some kind of possession of it.