It's completely anonymous. Even if they don't take the hint, you'll feel better.
-- Preparation H for an 'inflamed a$$hole'
-- An athletic supporter for somebody who failed to support you
-- And, um, I forget the third thing.
I wrote 'em and asked if they would send a round of .45 ACP with my stepfather's name engraved on it. [He was straight from Grimm's fairy tales, and abused me and my brother for 12 years]. "Sorry, it might be taken as a threat," they replied.
"That was the general idea..."
No, I never really planned to murder him (just worry him a bit), and he (unfortunately) died in his sleep.
--Boris
If you want to let someone know that they break wind in public inconsiderately but you are reluctant to tell them in person.