Facebook CEO Cheryl Sandberg reports that the popular online community’s active membership surged from 90 million this past July to more than 120 million by the end of last month.

Speaking at Saleforce.com’s Dreamforce conference this week, Sandberg confirmed that, “We got more [members] in the last three months than in the first three years of our existence.”

Sandberg was at the conference to tout Facebook’s partnership with Salesforce.com, under which Salesforce.com customer relationship management applications will be able to run on Facebook.

Observers say the alliance could bring a new ‘business’ face to Facebook, which has, until now, been predominantly an entertaionment-oriented community.

The jury is still out, among users, as to whether business activity in the community is a good thing or not…