I think it's quite possible that LE will be able to determine where the photographs came from that Sharon found in her yard. A lot of people aren't aware of all the secret codes hidden in the everyday things in our lives. I saw a special once about this on MSNBC or CNN, and it's all very interesting (and a little scary!).
Here's a website that goes in detail about this subject (it's not just printers etc!), but more specifically this link provides information about how some printers code print-outs with detailed information, including serial numbers, etc.
http://www.eff.org/press/archives/2005/10/16
Those pictures and letters may very well have some type of identifying information on them.
If they can i.d. the serial number, they can go back to a specific store and find out who bought the printer if they didn't pay cash. If a store printed those pictures, that info could very well be found as well.
Things to remember when you *think* you are being anonymous.
I also heard Sharon say the letters were on red (or pink?) and green paper. That alone tells me someone is not doing this out of the kindness of their heart. That's almost a taunt using Christmas colors. How sad.
