It turns out love was a factor in Facebook opening a Seattle office, perhaps even more than the area's technical talent.

The story begins with Ari Steinberg, a Facebook engineering manager, and his wife, Daniela Witten, a Stanford grad student.

When Witten began looking for a job teaching biostatistics, the couple decided to think about places where Facebook could someday open an office.

Steinberg was going to follow Witten, thinking he could work remotely for a while.

That was a possibility in Seattle, after Witten ended up landing a job this year as an assistant professor at the University of Washington. Then the company decided there was a bigger opportunity.

"I was definitely ready to come up here after that," Steinberg said. "We realized it was a good place for the company to start an office."

The backstory emerged at an unusual catered reception Seattle Mayor Mike McGinn held this afternoon at City Hall to welcome Facebook to town. McGinn left before the speeches ended, missing out on the open bar and hors d'oeuvres. (Here's Steinberg and Witten at the event)

Facebook and McGinn's office announced the company's Seattle plans on May 5. It's characterized as the company's first satellite engineering office in the U.S., although the company earlier opened an engineering center in Hyderabad, India, and a sales office in Austin, Texas.

The company isn't saying exactly where in Seattle it's going to locate, but it's looking for a 7,000-square-foot space that will initially accommodate three or four engineers moving up from Palo Alto, where Facebook is based. In a year or so the office could grow to 30 employees, although there's no firm number or growth plan, Steinberg said today.

"We would like to hire as many as we can find that fit the bill," he said. "Thirty just seemed like a nice round number."

Steinberg, 27, also graduated from Stanford and has worked for Facebook for four years. He's been working on the social network's feeds -- the home page team -- but that doesn't mean the Seattle office is going to focus on that particular project. Its role is open and will depend in part on who is recruited, but Steinberg said the plan is for the office to collaborate closely with headquarters.

Asked why McGinn held a red carpet reception for a relatively small office, Stephen Johnson, Seattle's acting director of economic development, said Facebook "is really aligned with his vision for economic development."

But the main reason was that Facebook asked the city for help introducing itself to Seattle, Johnson said. As if it needed the help.

Another factor in the relocation was Seattle's Hadi Partovi, the former MSN manager, startup founder and engineering manager at MySpace. Partovi is a longtime adviser to Facebook and is now consulting with the company's engineering management.

Facebook has a few other friends around here. Microsoft is a business partner and investor, RealNetworks is a major developer of Facebook applications, and Facebook is working with the state of Oregon on tax breaks for its first datacenter, located in Prineville.

Still, Seattle is lucky that Witten didn't take a job at the University of Oregon.