Twitter sees itself as the digital incarnation of the town square, eliminating time and distance as barriers to unfiltered communication among citizens. In this role as the world’s unofficial open idea exchange (in 140 characters or less, of course), the company is finding that governments, law enforcement agencies and even its own Twitterverse are increasingly holding it accountable for how people use its microblogging service.

The social network appears to be taking this newfound responsibility seriously. During a Webcast conversation on Wednesday with Brookings Institution Senior Fellow Jonathan Rauch, Twitter CEO Dick Costolo discussed how his company responds to this growing scrutiny. He also talked about Twitter’s attempts to help users filter the fire hose of information they face each day as well as the pros and cons of pseudonymous tweeters.

Although he declined to comment specifically on the U.S. National Security Agency’s PRISM digital surveillance program, Costolo articulated Twitter’s stance on cooperating with government and law enforcement requests. “When we receive a valid, specific request in the countries [where] we operate, we will honor it,” he said. “Those that are not legal and valid, we will push back on.” Twitter is conspicuously absent from the list of tech companies—including Apple, Facebook, Google, Microsoft and Yahoo—accused of complying with the NSA’s requests for user data.

Twitter’s computer servers—like those of many Web sites—automatically record information generated by users. This may include a user’s IP address, location, mobile carrier and the device used to access the Twitter account. The company says it deletes this data or removes any common account identifiers—such as username, full IP address or e-mail address—after 18 months.

In the past year Twitter has begun to publish a biannual transparency report highlighting trends in government requests it has received for user information and content removal. (Google publishes a similar report). “We would like more companies to do this,” Costolo said. “Our users have a right to know when their information has been requested so they can fight the request if they wish.”

The Twitter report also indicates how the company responded to those government requests, which have increased steadily in the past year. Twitter received 849 such requests during the first half of 2012 and 1,009 during the second half—the lion’s share coming from the U.S. government. The latest report will be published in a few weeks. “When you don’t have any idea what information is being requested, you can only imagine what the government wants,” Costolo said. “More organizations should participate in these transparency reports because they help people understand exactly what is going on. Then you can disagree or agree with the specifics rather than assumptions.”

Mobile devices offer people a means of ubiquitous online communication—they also give companies a way to track those people using the devices’ geolocation capabilities. This raises questions about privacy that have been little more than an afterthought to this point, Costolo noted. Still, he pointed out that there’s no need to be fatalistic about the future of privacy, given that Twitter and many other social networking sites require users to opt in for features such as geolocation that broadcast a user’s whereabouts whenever they log on.

One of Twitter’s main goals, not surprisingly, is improving its ability to curate important events so the most relevant information is easy to find. “Right now you get the reverse chronological order of the tweets, but it would be nice to see a graphic of spikes in the conversation,” Costolo said. “It would be nice to be able to scroll back to [a] particular moment.” He likened this capability to a digital video recorder for social media that would help Twitter users more quickly get to the substance of a conversation.

Twitter has experimented with ways to filter out some of the background noise that obscures more relevant reporting and reactions to important events. “We tried a couple of things during the [London 2012] Olympics, such as curating tweets from the more important sources [such as broadcasters and analysts], but it felt like you were in a very quiet studio,” he said. “You lost that roar of the crowd that makes [Twitter] the public town square. We became more of an aggregator.”

Twitter is also looking at ways to preserve user anonymity without facilitating troll-like behavior where pseudonymous account-holders use their tweets to harass other users. Anonymity is especially important when Twitter is used as a tool for social change, with protests in Turkey being the latest example, said Costolo, who did not comment further on the situation in that country. The ability to use a pseudonym is crucial to enabling open political discourse, he added. “You can use our platform to say what you believe.” Turkish Prime Minister Recep Tayyip Erdogan has condemned Twitter as a way to spread lies about his government, which has asked Twitter to reveal the identities of users who posted “messages deemed insulting to the government or prime minister or which flouted people's personal rights,” according to Reuters.

Anonymity does create headaches for Twitter beyond governments demanding user identities, Costolo acknowledged. Pseudonymous tweeters are a problem when they engage in cyber bullying and can be particularly vicious in what they say about celebrities and other public figures. He added, “We have to do a better job of filtering out egregious and repeated harassment.”