Their problem is...often they are inappropriate [content] to the thread in which they are posted....and like most things....once is 'cute'...but a page full of responses with their 'sigs' is something worse than tedious....to have to wade through.
When/where I could use one....it was a BIOS error...."Keyboard not found. Press F1 to continue."
I often use a quote from Raistlin Majere of Dragonlance.
"What do I see? I see time as it affects all things. Human flesh whithers and dies before my eyes. Flowers bloom, only to fade. Trees drop green leaves, never to regain them. In my sight, it is always winter, always night. ~ Raistlin Majere"
It doesn't often fit every occasion, but I like it none the less.