Lars Rasmussen shows off Google Wave in May 2009.

One of the lead engineers behind Google Maps and Google Wave has left the Web powerhouse to get into the thick of the "compelling" action at Facebook.

Last Friday, Lars Rasmussen said goodbye to his six-year career at Google' he'll start his new job at Facebook in December following a vacation. The noted Sydney, Australia-based software developer explained why he jumped ship in an interview with the Sydney Morning Herald.

"It feels to me that Facebook may be a sort of once-in-a-decade type of company," Rasmussen told the Herald. "Obviously they've already changed the world and yet there seems to be so much more to be done there. And I think that it's the right place for me to be."

The size of Facebook versus that of Google was another reason for the job hop, according to Rasmussen. Comparing Google's 25,000 employees to Facebook's 2,000, Rasmussen told the newspaper that Google was becoming unwieldy and said he felt that Facebook's smaller size would make it easier to get things done.

"The energy there is just amazing, whereas it can be very challenging to be working in a company the size of Google," Rasmussen said in the Morning Herald story.

On a purely financial basis, Rasmussen also said that the Facebook offer was too good to refuse, calling it "much more compelling both financially and in terms of the work there."

Rasmussen, who said he received the "compelling personal pitch" from Facebook co-founder Mark Zuckerberg, defined his new job description as "come hang out with us for a while and we'll see what happens," which he called "a pretty exciting thing."

Confirming the news, a Facebook spokesman sent CNET the following statement:

"It's true that Lars Rasmussen has joined Facebook. Lars has a knack for building elegant, powerful products that people love. We're thrilled he'll be part of Facebook's world-class engineering team to help design transformative technologies that will improve how people connect and interact online."

Rasmussen joined Google in 2004 after his start-up mapping company was acquired by the search giant. Together with his brother and two fellow Australians, he turned this acquisition into the creation of Google Maps, which proved a huge success. But the software developer's most recent project didn't turn out quite as well.

Rasmussen and his team were the brains behind the recent Google Wave project, which the company abandoned in August due to low user interest and confusion over the purpose of the tool, even within Google itself. Rasmussen himself seemed a bit unclear over Wave, telling CNET at the time, "It takes a little getting used to. We're still learning how to use it."

With Wave one of his "pet projects," Rasmussen admitted to the Sydney Morning Herald that he felt Google may have reacted too quickly in ditching the effort.

"We were not quite the success that Google was hoping for, and trying to persuade them not to pull the plug and ultimately failing was obviously a little stressful," he said.

Rasmussen joins other prominent players who've left Google amid various complaints. Last year, for instance, Google visual design leader Douglas Bowman exited the company, venting in a blog post that the creative process of Web design at Google was becoming too confined and controlled by data analytics.

At Facebook, Rasmussen will also also cross paths with two former Google colleagues. Facebook's Chief Technology Officer Bret Taylor was part of the Google Maps team, while Carl Sjogreen, now a product manager at Facebook, was also involved with Google Maps.

Updated at 9:40 a.m.: Added comment from Facebook.