How can I remove the key labels from my Apple Wireless Keyboard?
You can't erase the print, because the "foreground" and "background" are two colors of plastic that comprise the entire keycap.  That's so the print doesn't wear off.

You could cover the print with paint or a sharpie, but that would wear off.

Stickers feel bad, and do wear off (I had this problem in an Avid video suite).

Some blank-keycap keyboards are for sale, e.g. http://en.wikipedia.org/wiki/Happy_Hacking_Keyboard, but they're not exactly what you want.

Some vendors sell replacement keycaps, like http://www.ebay.com/itm/281064247677 , but they may not have blanks, because they get theirs from other Apple keyboards instead of making them themselves.

The best, but not quick-and-dirty, solution would be to take RTV molds of the original keycaps (pry them off like this: http://store.apple.com/us/question/answers/product/MC184D/B/1/QK2AFXHXKKA2J7AXA ), and then mold your own keycaps from scratch.