BoomTown was as surprised as anyone when longtime Silicon Valley Web music entrepreneur Dave Goldberg said in May that his next move was going to be investing in and running an online survey company with the unusual name of SurveyMonkey.

Most expected the former Yahoo music head to land at an entertainment or media giant, running its digital operations.

But it is at SurveyMonkey where Goldberg has swung himself and he has now made good on his promise to open a Silicon Valley office of the Portland-based start-up.

But Goldberg’s background does not suggest an interest in digital clipboards and checking boxes.

He joined Yahoo (YHOO) in 2001 and headed its global music operations after it bought a company he co-founded in 1994 called LAUNCH Media.

Previous to that, Goldberg was director of marketing strategy and new business development at Capitol Records in Los Angeles.

After leaving Yahoo more than two years ago, he worked for a while as an entrepreneur-in-residence at Benchmark Capital and told me he was attracted to the online survey creator most of all for three key reasons:

It’s profitable. It’s an open field. And, it’s much more of a consumer product than people realize.

That’s presumably why he also put up some money to become a minority investor in SurveyMonkey.

It was part of a deal in which Spectrum Equity Investors and others, including Bain Capital Ventures, acquired a majority interest in the company.

Since it was founded in 1999 by Ryan Finley and Chris Finley, who remained minority investors and working at the company, SurveyMonkey has become the largest such survey company online, with competitors that include Zoomerang and Constant Contact.

SurveyMonkey–which has signed up two million users, with six million surveys created and 200 million responses completed–charges a variety of fees for premium versions of its service, sitting between expensive software packages on one side and free, featureless Web surveys on the other.

Here’s a video interview I did with Goldberg last week about all this and more, as well as a tour of the new SurveyMonkey digs in Menlo Park, Calif., in former CBS (CBS) Interactive space: