That's quite an achievement in a region that views most celebrities with suspicion.
"Many folks I've met from the talent side have shown passing interest at a transactional level, but have quickly scurried away when there's no immediate deal with instant payoff to be had," says Tim Chang, a partner at Norwest Venture Partners in Palo Alto, Calif. "Hammer has authentic interest in what's going on."
It's a reputation developed during the course of nearly two decades, during which Hammer has invested in or advised dozens of companies. He helped Pandora founder Tim Westergren prepare for meetings with music executives when the service was still called Savage Beast. He gave marketing advice to Salesforce.com. He visited YouTube's offices when it was still located above a pizzeria in San Mateo, Calif.
More recently, Hammer has entered the business as co-founder of dance-based video network DanceJam, which Purevideo (now part of Source Interlink Media) acquired in 2009.
"Anybody in the Valley who invests around the commodity of music on the digital side, they know how to reach out to me," the Oakland, Calif., native says. "It's a very, very small community up here. I'm usually just a text away."
In Silicon Valley, Hammer's rise and fall as a hip-hop star isn't seen as a mark of shame or ridicule, but as a valuable experience worth learning from.
"People are a little bit less judgmental here," says Geoffrey Arone, Hammer's DanceJam co-founder and a former entrepreneur-in-residence at Bessemer Venture Partners and Battery Ventures. "For all you hear about these great companies, remember the majority of them fail. But you try again. So there's something about the psychology here where no one is going to judge you about any challenges you had in the past, but more like, 'What did you do to succeed?' and 'How can we repeat it?' "
Today, Hammer is working with about a dozen startups. He's an investor and adviser to Bump Technologies, a Mountain View, Calif., developer that makes an app to enable users to share contact information by simply touching their iPhone or Android handsets together. He's an investor in Square, a San Francisco mobile payment service provider founded by Twitter co-founder Jack Dorsey. And Flipboard, the buzzed-about iPad social magazine app, premiered Hammer's single "See Her Face" in February, the first time the company had featured music in its app.
Notice how none of them is a music company?
"Music is definitely not first," Hammer says. "I'm interested in companies that can have a global impact on enterprise in general; things that can make your connected life more interesting and easier. But always, I look for opportunities to support and expand the music business model or reinvigorate the music business model."
For instance, the former rap star, who has 2 million-plus Twitter followers, hints at "big announcements" in the coming months related to new music files and formats to help artists monetize music on the social Web.
He's also begun advising music executives on how to best approach companies and investors in the Valley. Specifically, he claims to be working with "the highest levels of the music industry" on the creation of a "consortium of leadership" to figure out how the music industry can launch the next important social music service.
"They're somewhat taken aback by the development here in the Valley," Hammer says. "The developers are coming up with the ideas of how to better maximize music."
And he wants to show other artists, by example where possible, how they can expand their creative activities into new formats. "A lot of musicians and artists are shortchanging themselves because they have so much to offer other than just the song," he says. "Music is not just a song."
Just as artists extended their craft into music videos during the heyday of MTV, so should they be exploring new formats like social games, interactive technologies, and mobile or iPad apps. Hammer is experimenting with these areas himself, he says, having recorded and stored more than 300 tracks in his free time.
So does that mean we may see a comeback?
"Why not?" asks Hammer, who turned 49 in March. "Quincy Jones was 50 when he produced the 'Thriller' album. It's not unprecedented."