Bills in each house of the California legislature to ban paying circulators on any basis except hourly are both advancing. AB 1947 passed the Assembly Elections Committee on March 21. SB 1394 passed the Senate Elections Committee on April 3. Both bills apply to initiative, referendum, and recall petitions, but not to independent presidential candidate petitions nor petitions to create a new party.
Governor Jerry Brown vetoed a virtually identical bill in 2011.
The Senate Committee analysis has an excellent list of cases in which similar laws have been struck down. See it here. Click on the link.