I just came up with this idea based on my personal needs, but i think it's something useful in general.
Sometimes my users violate the TOS of my website. In these cases i send them e-mails informing them and tell them that if it happens again ill ban them etc. Generally, the best option for these cases (for me) would be to ban them for X days (let's say 5 days).
Problem is that i have many users, many registers daily etc. So i can't ban someone for X days, because then i will have to keep track when to remove the ban. And this might be happening often and for many user, so not easy to handle.
Also it would be great to be able to give a reason for the ban, and once you ban someone, he receives an email with info about ban (period, reason etc), and another email once ban lifted.