Social commerce and group buying has become increasingly popular these days, on Tuesday, The New York Times reported that Groupon received an investment of $135 million dollars from Digital Sky Technologies. Additionally, last month, another group buying website, LivingSocial, received an investment of $25 million dollars. With investors eager to back companies in this space, the volume of visits to this nascent category increased 72x year-over-year.

Groupon and LivingSocial currently capture nearly all of the visits within the custom category of 8 Group Buying websites, although there have been new entrants to the category hoping to capture an audience as well.

The top referring website for Group Buying websites last week was Facebook with nearly 32% of the total upstream traffic to the category. All of the group buying websites are leveraging Facebook in some capacity, such as the use of Facebook logins to access the websites or fan pages. Email websites are also important drivers of traffic for the deal alerts and comprised 4 of the top 10 websites driving traffic last week.