Meagan Cignoli's eye peers through a veil of cotton balls. In stop-motion bursts, her face emerges. The vignette lasts mere moments, but on Vine, the social network that lets users upload six-second clips, this is how a star is born.
Cignoli, 32, is in the vanguard of so-called Viners using the eight-month-old service to build a lucrative following. When Facebook's Instagram launched a similar video feature three months ago, some thought Vine, which is owned by rival Twitter, was toast. So far that hasn't been the case. Just as YouTube has launched Saturday Night Live careers, Vine is increasingly minting its...