Parker's donation was reported in Proposition 19 campaign finance filings this week.
And he's not the first big Proposition 19 donor with ties to the social networking site. Facebook co-founder Dustin Moskovitz gave $20,000 to the campaign and has contributions $70,000 overall.
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Neither Parker nor Moskovitz are still with Palo Alto-based Facebook, but both still have ownership stakes. Recent estimates put the value of the privately held company as high as $33.7 billion.
"What's interesting here is that (Parker) is a member of the generation that really gets it," said Stephen Gutwillig, a spokesman for the Drug Policy Alliance, the main beneficiary of Parker's contribution. "We think he's pivotal to the future of drug policy reform in the country."
The 30-year-old served as Facebook's first president and helped transform the company from dorm-room project to big business. Parker and Moskovitz have become household names since the recent release of "The Social Network." The film chronicling the contentious origins of Facebook was No. 1 at the box office last week.
At age 19, Parker helped develop Napster, the music-sharing software that turned the recording industry upside-down. He is now a partner at Founders Fund, a Silicon Valley venture capital firm.
Parker did not immediately respond to e-mails seeking comment.
About $1.5 million of the $2.4 million raised so far in support of Proposition 19 has come from the measure's main sponsor, Oakland medical marijuana entrepreneur Richard Lee.
The only other six-figure donation not from Lee came from adult entertainment entrepreneur Phil Harvey, who gave $100,000.