Matt,
I'm noticing today and other days recently that there have been a lot of instances of users posting two and even three identical images at a time. My guess is this has to do with the very slow uploading times some of us have been experiencing. In fact, earlier today I posted a double image. The load was so slow that I stopped it and restarted it. Later, I found two identical images in my gallery, one with the original caption and the second with a revised one.
I deleted that picture and have deleted some of the other duplicates I've seen, but there are surely many more.
Based on what happened to me today, I think pictures are uploading but are on the site before the user gets the confirmation, causing him or her to try again.
I'm just bringing this to your attention.