Well, nothing really. Lightning addresses are practically anonymous, which is a good thing. You can also add other peoples email addresses to random mailing lists if you wanted. Its just a dickish thing to do. We've already noticed people trying to take advantage of the system in other ways, but that is to be expected, and we'll be countering abuse if and when we see any.
This can also work for subscription:
Is there no way to unsubscribe?
For example, for mail subscriptions, there are laws that you must include an unsubscribe button. Obviously, LN is not SMTP. But I just wanted to mention this since the laws might be a source of inspiration for good UX :)
edit: looking at your site, I found this:
Can I remove my address from EagleSats? Certainly. Just send us an email to support@eaglesats.com or DM us on X with your Lightning address and LNURL and we'll remove you from the payments list.
I think having to send you an email or DM you on X is too much friction. Why is this not automated like subscribing?
Yeah good point, we'll prioritize this feature.