From SF Gate:
Supporters of the measure slammed the veto.
"This is a setback for reform in California," said Justine Sarver, executive director of the Ballot Initiative Strategy Center. "The measure would have eliminated a powerful incentive for fraud while protecting Californians' ability to participate fully in direct democracy."
Maybe they shouldn't be surprised -- the governor may have given a hint at his position last week when he mused, in response to a question, that the bill could make initiatives such as the one he is planning on taxes, more expensive.