This is a form I had a lot of fun with, and intend to do more of.
"Erasure is a form of found poetry or found art created by erasing words from an existing text in prose or verse and framing the result on the page as a poem. " - Wikipedia
Now, I don't know where this form came from, but it reminds me strongly of Rauschenberg's erased Willem de Kooning, minus the scandal. We commonly print thousands of genuine copies of books, and only one genuine copy of paintings, but the act of losing content does tug faintly on the heartstrings even if you're only defacing an old book of vapid children's poems. The price of progress.
Also related is The DaDa Vinci Code, where someone is making erasure poetry out of the pages of the Dan Brown novel, and doing a very good job of it.