I get a very small kick out of marking unsolicited PR and commercial emails as spam:
Gmail
I never knew what this actually did - indeed, I would often continue receiving emails from a sender I marked as spam - until this weekend when I spoke to an email marketer at a big corporation. It turns out it's a very big deal for email marketers, and too many spam reports led to a major campaign getting shut down at her company.
Specifically, an account will be locked if above 0.5% of emails from it are marked as spam, according to email marketing company Campaign Monitor.
Here's how companies keep track of that number:
