Is it so far fetched to compare these two famewhores? Let's look at the obvious facts, in no particular order.
Both dropped out of school.
Both got famous at an early age.
Both had men marry them for money and fame.
Both seem to need to go to the plastic surgeon from time to time.
Both have two children.
Both have dabbled in unorthodox religions.
Both are addicted to fame.
Both have the paparazzi on speed dial.
Both have strained relationships with their mothers.
Both have close almost too close relationships with their sisters.
Both have careers that are failing and/or faulty.
Britney listened to Keith Urban music while in rehab.
Nicole was responsible for ruining Keith Urban's music and driving him to rehab.
Both say very questionable things to the media that lead to questions about their stability.
Both have children that are being raised by their fathers.
and it goes on and on
Yes there is a vast age difference, Kidman is now over 40 and Spears is only 25, but both in this writers opinion, are two train wrecks we can't help but watch.
Did I mention they both have cellulite?