Mine would be a 'Start' button on my forehead

I'm puzzled by the fact that temporary tattoos haven't become a popular item. I know a few people who like their tattoo, but acknowledge that they'll look terrible eventually. I also know people who would love to get a tattoo were it not for the 'will-look-terrible-eventually' or 'may-no-longer-be-appropriate' turn of events.

So why haven't temporary tattoos taken off? Think about it, you can apply the symbol / phrase / picture du jour on your chosen body part and perhaps once it has worn or is no longer en vogue, you can erase it somehow and start a-new. Wouldn't that be neat?