if someone knowns your email address and that you've confirmed it, then yes, that someone could set up more, but the limit is 10.

If that ever happens to you, you could: 1) pause the unwanted alerts, and remove some only when you need new ones. 2) if you panic, use the "unsubscribe" button that will block any future emails to your address.

Having such a low barrier of entry does not come without tradeoffs.