The only risk is if someone knows that you’ve programmed your phone to do something dangerous when in range of a particular publicly available tag. Then that person could, in theory, copy the number from that tag and rebroadcast it… but their phone would have to be very close to your phone (or they’d have to have some sort of highly directional NFC antenna). But these tags can be relatively smart. That is, they can use cryptography to exchange their ID’s in a way that makes it difficult if not impossible to steal the ID and re-transmit.

In the case of a credit card, the problem is that the plastic credit card has no way to prompt you to authorize the transaction… so it just transmits your CC information to whoever prompts it. Here, you’re not going to walk by someone’s phone and convince Google Wallet to start up and start dishing out credit card info.

I’m not entirely sure capabilities of this, but i know this is an draw back of nfc credit cards – where someone can get close enough to you and steal the card number through the nfc capabilities… atleast so I’ve heard

But I don’t think that’s built into the TecTiles configuration tool (which probably assumes screen is always on). That would have to be an addon — a checkbox like “only do this task if activated while screen is on.”