Gag is unpopular and underrated. A lot of people do not know about it. When I mention it to someone I have to explain to them exactly what it is.
I discovered gag by typing a question in google. Almost the same exact question came up that someone asked on this site. After reading the question and its answers, I decided the site looked pretty cool and to join.
Nobody I know uses this site and I have told them about it, they just say "meh"
I discovered it because I was asking a question on google, then I found an answer linking it to this site. I wanted to ask a question of my own so I signed up but I had no idea I would ask a second one, let alone become a level 8 user :)
Found it when I needed help with a bad break-up. I probably googled some question about how to pick up the pieces. I was an awful mess at that time... Yet I found some solace here. It was refreshing to know I wasn't alone in my pain. Turned out some of our fine members had profound and enlightening advice on how to get through that rough patch. That was 2 years ago or more I think.