Note: they collect not only the information you provide yourself, but also from the cookies they store on your computer and the information stored on your browser.
And this is what they do with that information:
We engage certain trusted third parties to perform functions and provide services to us, including, without limitation, hosting and maintenance, customer relationship, database storage and management, and direct marketing campaigns.
We will share your personally identifiable information with these third parties
Twitter may sell, transfer or otherwise share some or all of its assets, including your personally identifiable information, in connection with a merger, acquisition, reorganization or sale of assets or in the event of bankruptcy.
When you visit the Site, our servers automatically record information that your browser sends whenever you visit a website (“Log Data” ). This Log Data may include information such as your IP address, browser type or the domain from which you are visiting, the web-pages you visit, the search terms you use, and any advertisements on which you click.
we may use your contact information to market to you, and provide you with information about, our products and services, including but not limited to our Service.
we will collect your cellular phone number account information
Now there’s nothing really odd about this, most websites collect some data on their users …but it’s what they do with that data that should concern you.
And apparently Twitter has no objection to collecting as much information about you as is legally possible from as many sources as they can and no objections to sharing that information with third parties or using that information in their own direct marketing campaigns.