Limited marketplace offer notifications

A new unpopular feature that nobody asked for: I've limited the number of automatic watchers you can set for offers on the marketplace.
On the module detail pages is that button Notify me if someone offers this module for sale. Standard users can sign up for 5 module notifications, while Unicorn users can set up to 2500 watchers.
The reason for this is that the mail server has been blocked several times due to excessive traffic, causing important features such as user messaging and optin registration to stop working.