As Twitter’s growth explodes, speculation has intensified about whether the service can be profitable. Twitter’s online traffic, excluding cellphones, surged to nearly 9.8 million unique visitors in February from 6.1 million in January, according to comScore.

In pursuit of revenue, Twitter faces the same challenge that has dogged social-networking platforms like Facebook. If advertisers can tap into its network free of charge, why would they pay the company to do so?

Twitter co-founder Biz Stone says the San Francisco start-up is watching the outside initiatives closely as it prepares to launch its own fee-based services this year, but doesn’t view them as competition. “We want to work with those companies that are already making an effort,” he says. Mr. Stone says Twitter recently hired a product manager to oversee the development of commercial accounts. The accounts would offer users more features in exchange for a fee, but Mr. Stone says Twitter hasn’t set a launch date for them, according to the wsj .

My thoughts are that there are two groups of people using Twitter’s search API: personal, and commercial. Personal users use it for fun, low hits, personal websites, little mashups that don’t make money, and commercial users try to monetrize it, like those mashups that will charge for fee-based services, or listening platforms that monitor brands, sentiment, behavior on a mass scale… these companies would be happy to pay for the API use … Isn’t that simple? I’m sure they’ll figure it out.