The nature and scope of the project required financing from a large venture-capital firm.

And unlike a traditional venture-capital firm, Avalon usually creates companies from scratch, rather than financing would-be entrepreneurs.

Some friends worried that it would suffer, said Mr. Schmidt, whose father founded one of the first venture-capital firms.

Eight years earlier he and Arthur Rock founded Davis & Rock, one of the nation's first venture-capital firms.

The second involves charities creating nonprofit venture-capital firms ("Virtual Pharmas"), which look for promising drug candidates and then push drug development through contracts with corporate partners.

Mr. House, who has been running his own venture-capital firm, Venturehouse, has tried to sell his trophy home before, according to one Birmingham Realtor.

The rest was held by venture-capital firms.

H.M.C. has also spread its investment tentacles into 68 private equity and venture-capital firms and seeds new investment funds too.

It was ranked as the 10th-best city in the world to launch a tech startup, according to a 2012 list compiled by Finaventures, a California-based venture-capital firm.

The company's largest outside shareholder is New York-based venture-capital firm Insight Venture Partners.