We both own my content
Given your legal language below, twitter effectively jointly "owns" my content. In other words, anything I can do with my content, twitter can too. You might want to change your "tip" to reflect this.
Currently the tip says: "This license is you authorizing us to make your Tweets available to the rest of the world and to let others do the same. But what’s yours is yours – you own your content." When told they own something, most non-lawyers assume that have EXCLUSIVE rights of ownership. That is NOT the case with twitter content. Twitter effectively has ALL the ownership rights to my content that I have. Twitter can use or sell (license) my content any way I can.
I think your "tip" should make that clearer. How about: "This license is you authorizing us to have all the same rights to the content that you have. Your content is twitter's content -- we both effectively own it."
You retain your rights to any Content you submit, post or display on or through the Services. By submitting, posting or displaying Content on or through the Services, you grant us a worldwide, non-exclusive, royalty-free license (with the right to sublicense) to use, copy, reproduce, process, adapt, modify, publish, transmit, display and distribute such Content in any and all media or distribution methods (now known or later developed).