Looks like the venture funding is still flowing for Facebook applications. The immensely popular Friends for Sale application has received $4 million from Lightspeed Venture Partners. At its basic level Friends for Sale doesn’t really have much of a business model but they are currently one of the most popular games on the site. So what does this new round of funding mean? It means that we have a new serious competitor in the world of social gaming alongside with Zynga and Social Gaming Network.

According to Justin Smith it was a “healthy double digit” valuation. Double digits? I’m assuming they mean in the double digit millions meaning that they probably gave away a large portion of their business in this first round of funding. $4 million can go a long way for a team of developers though and this adds more validity to the rapidly growing social gaming industry.

Take a look at Adonomics and you’ll see that Friends for Sale is the 6th most active game on Facebook currently. According to Alex Le, one of the founders of Serious Business, which owns Friends for Sale, this game is one of the “first in a series of games build directly around your relationships with friends.” According to Techcrunch, “the company could grow to 12 engineers without raising any financing.”

Looks like the team over at Serious Business Inc. have some serious plans for large expansion. It will be exciting to see what games the company rolls out in the near future.