Know any bands before they went big?

Vampire Weekend.
Fun. They had just come out with "Aim and Ignite"
Technically not a band but Katy Perry and Christina Perri

Does the bands that follow me on Twitter count? I know Consider Me Dead has grown a huge fan base in the past few years. There's also the band Hello Cleveland that was getting popular. I think they are making music again.

Farewell My Love, Fall Out Boy, Black Veil Brides (I guess... kind of on the edge, really)...

I used to talk to Robby from FML a little back before they put out "A Dance You Won't Forget" and we'd swap posts on Facebook advertising each other's bands. Fall Out Boy I saw in a tiny venue opening for American Hi-Fi and then, a few months later, opening for Gob before their first album came out when I was in middle school. Then BVB my bandmate and ex-boyfriend has known since Andy was trying to get the band going in Ohio and they planned a tour for both their bands that my ex's band had to back out of at the last minute, so by the time I had heard of them I think WSTW was just coming out, so it's more him who knew them before they were famous than me.