If the takeoff weight is underestimated, rotation will be done too early and may result in a case of tail strike.
One example of such mistake is a 747-400 (F-HLOV) in 2006 (case 8 in this study). The crew entered ZFW for TOW (100 tons lower), VR was underestimated by 32 kts.
(source: The Aviation Herald.)
UA B744 tail strike on Sydney takeoff (photo may not be the actual May 7th 2010 T/O).
I wonder why such basic mistake may be done. Weight could be sensed in some way by the instrumentation, and crew entered values should be challenged if really different.
To prevent the crew from being forced (or tempted) to rotate the aircraft beyond the maximum safe angle, isn't that possible to monitor the T/O progress and in case of low performances alert the crew, and provide an opportunity to reject the T/O.
Airbus FWB embeds many security systems (compared to Boeing), this is surprising that they cannot prevent such T/O tail strikes. I'm sure there are good reasons, just asking to understand the difficulty.
Edit: Based on the answer from Marky Mark, who references the EK407 case, I checked a study published in the aftermath of EK407 tail strike: Take-off performance calculation and entry errors: A global perspective and noted this recommendation for 'TOPMS':
While the above recommendation does not preclude data entry and calculation errors relating to take-off performance parameters from occurring, Transport Canada (Department of Transport) agreed that a take-off performance monitoring system(s) (TOPMS) would provide a significant safety benefit. However, before regulatory authorities establish a requirement for the fitment of TOPMS, a certified system would need to be developed (Transport Canada, 2010).
Basically, a TOPMS, which assists pilots in determining whether to continue or reject the takeoff, can be defined as (Brown & Abbasi, 2009, p. 7).
Are TOPMS now in place?