It's clear that homelessness in San Francisco and other startup meccas is a growing problem. But whose problem? Salesforce founder (and Time magazine owner) Marc Benioff believes that tech company founders who made their fortunes in the city, and drove housing prices out of reach for most people, should do more to help the problem they indirectly helped create. And he's taking some of his wealthy neighbors to task for not doing more.

At issue is San Francisco's Proposition C on the ballot this election day. The proposed law would tax businesses earning more than $50 million a year an average 0.5 percent on gross receipts. The tax would bring in a projected $300 million that would be used to provide both permanent housing and temporary shelters for San Francisco's homeless, as well as mental health services. Benioff supports the measure. He has also contributed substantially to the Heading Home initiative to house 800 homeless San Francisco families by the end of next year.

Proposition C is similar to Seattle's ill-fated head tax, a $275-a-year-per-employee tax on businesses in that city earning more than $20 million. The City Council passed it unanimously in May and then repealed it in June under pressure from Amazon and Starbucks, among others. (Amazon actually halted work on a partially constructed office tower as an open threat to the city.)

In the same way, many of San Francisco's large employers other than Salesforce have come out strongly against Proposition C, including Jack Dorsey, co-founder and CEO of Twitter and founder and CEO of Square. Dorsey tweeted his opposition to Proposition C last week, noting that San Francisco mayor London Breed opposes it and that "I trust her."

The two billionaire CEOs got into a Twitter spat about the proposed law.

Other than to say he supported the mayor's plan, Dorsey did not answer questions about which (if any) homelessness initiatives he supports or has donated to. Stripe, another payment company and prominent San Francisco tech startup, is actually donating hundreds of thousands of dollars to the fight to stop Proposition C. Instead, it's backing an initiative that would make it harder for the city to block new development. 

Benioff told The Guardian that he's not surprised by Dorsey's apparent lack of generosity. Noting that there are 70 billionaires in the Bay Area, he said, "not all of them are giving money away. A lot of them are just hoarding it. They're keeping it. That's just who they are and how they look at their money."

Earlier this year, a San Francisco developer and entrepreneur named Justin Keller drew harsh criticism for an open letter to the city's mayor and police chief, complaining about the homelessness problem and how it made the city's residents feel unsafe. In it, he wrote:

I know people are frustrated about gentrification happening in the city, but the reality is, we live in a free market society. The wealthy working people have earned their right to live in the city. They went out, got an education, work hard, and earned it. I shouldn't have to worry about being accosted. I shouldn't have to see the pain, struggle, and despair of homeless people to and from my way to work every day.

Yikes. It's very clear that all San Franciscans, whatever their politics, are troubled by the widespread homelessness in their city. But what, if anything, are they willing to do about it? The answer to that isn't clear at all.