As the Facebook Platform continues to mature, larger app developers are swallowing up smaller ones in a race to create economies of scale and barriers to entry. Tonight, Social Gaming Network announced that it is continuing that trend by acquiring (fluff)Friends, one of the most popular Facebook applications, for an undisclosed sum.

Since its launch in May 2007, (fluff)Friends has become one of the richest and most well developed apps on the Facebook Platform. (fluff)Friends lets users adopt virtual pets, interact with their friends’ pets, and earn virtual currency to spend on things like food and customizable habitats. Founder and developer Mike Sego has regularly appeared at industry panels on issues related to social game design discussing the game’s unique combination of virtual world, MMO, and social game characteristics.

SGN was likely attracted to the robust economy within (fluff)Friends, which is driven by a rich combination of incentivized user interactions, offers powered by Peanut Labs, and direct virtual currency purchase via Paypal. SGN says (fluff)Friends has seen a 192% increase in revenue per spender and a 143% increase in spend per transaction since January of this year.

How exactly does the (fluff)Friends economy work? It’s pretty sophisticated. Here’s a quick summary:

How can players earn “munny”?

• By petting other (fluff)Friends – 5 munny per petting
• By inviting other Facebook friends to adopt a (fluff)Friend – 5 munny for each invite you send, and 25 munny for each friend who accepts
• By betting on (fluff)Races – payout based on odds – jackpots can be huge!
• By Challenging other (fluff)Friends to a (fluff)Race Bonus Challenge – 10 munny per win
• By participating in anonymous surveys – 200 munny signing up, either 100 or 500 per survey
• By selling Limited Edition items at the Limited Edition Shop – name your own price
• By exchanging Gold for munny at the Gold Exchange – 10 Gold for 500 munny

How can players spend “munny”?

• Purchasing (fluff)Foods to feed any Fluff from their (fluff)Book profile
• Purchasing new Habitats for your Fluff from the Habitats Shop
• Adopting Minis – miniature (fluff)Friends – at the Minis Shop
• Purchasing Decorations for your Fluff from the Decorations Shop
• Betting on (fluff)Races, and potentially winning prizes, trophies, and huge jackpots!
• Purchasing Limited Edition items at the Limited Edition Shop

How can players get “gold”?

If you enjoy (fluff)Friends and want access to extra special items and features, there is a premium currency, Gold!

Gold is available for purchase directly from (fluff)Friends. Transactions are made via PayPal in US Dollars at a price of $1.00 for each 10 Gold…

For each 50 Gold ($5.00) you either purchase or earn, you will receive a Golden Ticket, which you can trade in for one of the special MegaMinis below!

With the acquisition, (fluff)Friends brings over 1 million monthly active users to the SGN portfolio.

“We’re looking forward to joining forces with SGN to make (fluff)Friends a much greater gaming experience for our users,” said (fluff)Friends founder Mike Sego. “The SGN team is very creative and focused on building great games and great user experience, which is why we know (fluff)Friends together with SGN will be a powerful combination.”

Last month, SGN announced an investment by Bezos Expeditions. In May the company raised a $15 million Series A round lead by Greylock Partners and Founders Fund.