Tech billionaires Marc Benioff and Jack Dorsey clashed over a key law that could seriously impact the San Francisco homelessness crisis

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Twitter CEO Jack Dorsey opposes Prop C, a San Francisco measure which would tax the largest businesses to fund homelessness services.

• A San Francisco city measure, which is up for vote in November, has caused a stir among tech elite.
• Prop C would tax the largest businesses in the city in order to fund homelessness services. It's estimated to bring in between $250 million and $300 million in revenue annually.
• Salesforce CEO Marc Benioff is a strong proponent of the measure.
• Twitter CEO Jack Dorsey took to his social network on Friday to oppose Benioff's support, though Benioff was quick to respond.

Several of San Francisco's most powerful tech CEOs publicly locked horns on Friday over an upcoming election measure that would make the city's largest businesses pay a greater share of the bill for homelessness services.

In a series of back-and-forth tweets, Salesforce CEO Marc Benioff, Twitter CEO Jack Dorsey and the Irish-born CEO of Stripe, Patrick Collison, debated Prop C, a ballot measure in the upcoming November election that would raise taxes on large companies to help San Francisco deal with an intractable homeless problem. 

Benioff, who founded and runs the largest company in San Francisco, has strongly endorsed the measure, despite the fact that it could ultimately cost Salesforce millions of dollars in city taxes. Benioff has issued a public statement on Twitter, and bought ads in support of the measure.

The San Francisco Controller's Office estimates that the tax would bring an additional $250 million to $300 million in revenue to the city each year. The tax would impact to an estimated 300 to 400 local businesses, and applies to business with more than $50 million in San Francisco gross receipts as well as companies headquartered in the city.

In a carefully worded tweet on Friday, Twitter's Dorsey said that he disagrees with Benioff's active support for Prop C.

"I want to help fix the homeless problem in SF and California. I don't believe this (Prop C) is the best way to do it. I support Mayor [London Breed] and [Scott Wiener's] commitment to address this the right way. Mayor Breed was elected to fix this. I trust her," Dorsey sid on Twitter.

Stripe's Collison, who is Irish, voiced his support for Dorsey following the exchange.

The exchange highlights what has become a thorny and embarrassing problem in San Francisco, where the sight of tents, human waste and indigence provide a jarring contrast to scooter-riding techies who work for some of the most valuable companies in the world. Twitter has been a longstanding target of criticism because it negotiated a controversial tax break as an incentive for it to remain in San Francisco and move into its Market Street headquarters several years ago.

Breed, who was elected as mayor in June, has come out against the measure. In a statement she said that the city should do an audit of what it's already spending on homeless services before "we double the tax bill over night."

Benioff sharply responded to Dorsey and suggested that the Twitter CEO was not doing his part to curb homelessness.

"Which homeless programs in our city are you supporting? Can you tell me what Twitter and Square & you are in for & at what financial levels? How much have you given to heading home our $37M initiative to get every homeless child off the streets?" Benioff tweeted.

Here is the full exchange: