To fail at life, generally suck, or just be a hoe.
Britney Spears: Shave head. Rehab. Lose custody of kids to none other than Kevin Federline. Suck at VMA's. Attempt Suicide. Rehab. Repeat.
Jamie Spears: Be a lot better off then her sister. Then, completely ruin a Nickelodeon series by getting pregnant with a guy that was almost old enough for it to be considered rape.
So, in general, if someone accuses you of being Spears, you FAIL.
Guy: you suck, you're such a Spears.
Other Guy: I just died a little bit on the inside, thats the worst insult ever.