Â鶹ӰÊÓ

In a move that has sparked privacy concerns among social media users, Twitter is granting data mining companies access to comb its archives.

More than 250 million tweets are sent everyday, representing a treasure trove of personal data. Twitter says it's opening that data vault and selling tweets dating back two years to marketing companies.

Gnip Inc, of Boulder, Colorado and DataSift, based in the U.K. and San Francisco, are licensed by Twitter to pore through archived tweets as well as users' personal information such as where they live.

DataSift said it will release Twitter data dating back two years to its customers. Gnip said its information will encompass the previous 30 days.

Some prolific Twitter users have cried foul, arguing their 140-character posts weren't designed to help marketers build brand profiles.

Privacy specialists agree, saying social networks haven't been upfront about what they do with the information that users offer up freely.

"We tweet for a particular audience," privacy specialist Avner Levin told Â鶹ӰÊÓ Channel. "We don't imagine when we do that, that they will actually be used for market research purposes, so . . . (they) can learn more about me about me, about my segment, my age, about where I am, about what I prefer in a brand."

Twitter isn't the first social service network to mine user data. Google and Facebook also sift through their users' online information for marketing purposes.

In 2010, Twitter agreed to share all of its tweets with the U.S. Library of Congress. Details of how that information will be shared publicly are still in development, but there are some stated restrictions, including a six-month delay and a prohibition against using the information for commercial purposes.

That is where DataSift comes in. More than 700 companies are on a waiting list to try out its offering, DataSift CEO Rob Bailey told Reuters in an interview. Those who buy the data will be able to see tweets on specific topics and even isolate those views based on geography. Bailey likened the experience to holding a huge number of sporadic focus groups on brands or products.

For example, PepsiCo could look at what people in Oregon are saying about its Diet Pepsi Lime, or Tim Hortons could find out what people in Regina are saying about its new extra large-sized beverages.

Gnip, which offers the short-term data package, said the information collected -- which involves real-time viewing -- can also be used during natural disasters to help rescuers, to monitor illnesses such as a flu outbreak and to analyze stock market sentiment.

However, Levin, who is chair of the Ted Rogers School of Management's law and business departments, said social networks should be more upfront with users about how their data will be used.

Even though Twitter posts are intended for public consumption, Levin argued that users don't necessarily want their messages sold.

Twitter has said it won't provide marketers with deleted tweets or direct messages. Levin urged Twitter users to scroll through old tweets and delete the messages they don't want passed to marketers.

In Britain, the Twitter changes were criticized by some devout users. The Guardian's Grace Dent, who has 43,081 tweets under her belt, recently wrote: "I don't want the flippant utterances that passed through my head and on to screen since 2010 mechanically harvested and used to flog me tat.

"Twitter needs to stop presenting their product like a delicate, chirpy pale blue sparrow, then behaving like a giant, dirty, corpse-stripping vulture."

Levin urged social media users to think twice about what they post.

"The problem with the online experience is that we want to socialize with our friends and with our followers and share information with them. We don't necessarily want to participate in a lifelong focus group."