In a VentureBeat interview last week, co-founded Biz Stone described in greater detail Twitter's plans to launch a revenue model before year's end.

As in previous discussions, Biz Stone reiterated that Twitter would not charge users for existing usage habits; the company plans to launch a set of premium services, such as more detailed analytics or deeper CRM services, for which companies using Twitter may be willing to pay.

"It might be hard to tease out who is using the service professionally and who is using it for personal reasons, and then charge them for it," the co-founder acknowledged. "So the idea is to build a set of features that people are willing to pay for."

Differentiating the talk from previous promises, Stone assured VentureBeat that such services are already in first-phase testing with a select pool of companies. He also cited the possibility of creating a separate "commercial API" for business-oriented apps.

As an aside, Stone also said Twitter had been interested in purchasing social network aggregator Friendfeed, which was purchased for $50 million by sometimes-rival Facebook earlier this month.

Last week, Twitter announced plans to eventually add latitude and longitude data to all microblog posts published on the site — on an opt-in basis.