If you have donated blood, every 2-3 months they will send you an e-mail for a new donation cycle. That's fine. But if you don't respond, they will send another reminder. Then a text. Then they will call you.
Yes, you can just click the "Not this time" button, and click the reason for denying in their web portal, but sometimes you're busy.
I understand that this procedure probably nets them more donations, but the feeling of being lightly hounded never escapes me, and it makes me slightly less agreeable about donating, even if it would never be a reason for me to not donate.