Janis Joplin Syndrome is when a music group has a female singer that becomes just as if not more famous than the band she is in. Named after Janis Joplin who was originally a member of a blues revivalist group called Big Brother and the Holding Company. If you know anything about music history, you'd know that Janis left BBATHC after a 2-3 year stint with them to start a short lived but widely successful solo career.
70% of cases of JJS often end up with either the singer going solo (see The Supremes, No Doubt and Destiny's Child) or worse, the singer being the only original member left, somewhat like Axl Rose Syndrome (see Evanescence). Most of the time, all-girl bands are immune to JJS with a few exceptions such as the Bangles.
other famous cases of Janis Joplin Syndrome include:
Diana Ross from the Supremes
Gwen Stefani from No Doubt
Beyonce Knowles from Destiny's Child
Hayley Williams from Paramore
Amy Lee from Evanescence
Susanna Hoff from The Bangles
Tarja Turunen from Nightwish
The Strokes from new york. kicked the whole garage rock revival. known best for their album "is this it", and songs like "last nite" and "reptilia".
The White Stripes from detroit. has only two members but sounds like a thousand. the most successful of the 4.
The Hives from sweden. the most cartoony of the 4. they all dress in black and white and have had constant comparisons to the stooges in terms of performance.
The Vines from australia. they had only one noteworthy album. interestingly enough, the singer has asperger's syndrome, which has constantly got in the way of the band's touring. somewhat like the hives, the vines have had constant comparisons to nirvana for their stage performances.
guy 1: hey dude, who's your favorite band from the 4 the's?
guy 2: umm.... the vines i guess.
guy 1: really?
guy 2: hell yeah, have you seen the guy perform? he's insane!