The reason for starting a new bitcoin is simple:
We can assume that 50% of all bitcoins mined are either held by wrong persons, or are lost.
A lot of people are burned by the MtGox theft, therefore they have nothing to lose on switching to a new coin.
If we start to use a new coin the miners can use their hardware to switch over as well, and effectively abandoning Old Bitcoin.
The value of Old Bitcoin will drop to zero which will punish preminers, thieves and FBI.
Bitcoin holders that will be punished most:
FBI: 10%
Satoshi: 10%
Thieves (from MtGox and other sites): 20%
Lost coins: 10%
Total = 50%
What about the people and businesses that still hold bitcoins from legitimate purposes? Just because you personally got burned by Gox doesn't make BTC useless to everyone. Many of us still have skin in the game. If you would like to move another currency, feel free. But you're going to have difficulty rallying everyone else to abandon the investments they hold just because
YOU got burned entrusting your coins under the control of someone else.
Instead of moving to a new currency, how about practicing some of the security precautions that are posted in abundance all over the internet?