After a filing in 2007 based on its social network, Twitter was finally granted a patent on... well... Twitter. US Patent #8,401,009 grants Twitter the rights to how its service works.
When news came of the applications approval, Twitter co-founder, Biz Stone, tweeted "Look Ma, I'm officially an inventor." Does this mean that Twitter will begin suing other startup social networks or services that have similar functionality? Technically they could, but Twitter has a policy that requires its employees to vote before legal action could be taken.
"Like many companies, we apply for patents on a bunch of our inventions. We also think a lot about how those patents may be used in the future, which is why we introduced the Innovator's Patent Agreement to keep control of those patents in the hands of engineers and designers."