Sticky situation

I've always had a soft spot for stickers though I thought my older sister was slightly mad when she used to collect the stickers found on fruit - she filled a whole exercise book with them, no duplicates either! But this is possibly one of the most amusing sticker uses I've seen. I recently went on a visit to Eagle Heights (a bird and wildlife sanctuary with an emphasis on eagles) and this is what the visitors do on exit, graffiti a wall with their entrance stickers.
I wonder who went first and how long it's been evolving?
If you've done any good sticker spotting then share your stories here!