Is a rev limiter needed? What for?
Can it be taken off?

Well, it seems that GM played with different types of systems, but the latest of these will keep the top speed to something respectable and the rpm to something respectable so neither limit can be exceeded.

Earlier models just turned off the fuel rail at a certain speed and would not allow high RPM's in park.

Yeah mine is only when I'm in park or nuetral I can't rev past 4000. There is no need for me to because it's not like I'm racing with an 04 Sunfire LOL. But I just wondered the reasoning behind GM doing it! THANKS

Limit top speed, limit accidents and make it so the police can catch up to the crooks.

Limit RPM's. Limit engine damage. Keep engines from blowing up implies more reliable cars.

OK, it makes sense thank you!