I go updated terms of service from twitter, the following caught my attention:
How does Twitter determine which devices are associated with my account or device?
When you log in to Twitter on a browser or device, we associate that browser or device with your Twitter account. Whether or not you are logged in to Twitter, we may also receive information about your browsers or devices when, for example, that information is shared by a partner; you visit twitter.com; you visit third-party websites that integrate Twitter content; or you visit a Twitter advertiser’s website or mobile application. We may use this information, most commonly IP addresses and the time at which the information was received, to infer that certain browsers or devices are associated with one another or with your account. To learn more about the browsers or devices we use to measure and improve your experience, check out Your Twitter Data while logged in. To learn more about other browsers or devices we use to measure and improve your experience on the device or browser you are currently using, visit Your Twitter Data while logged out.
What does ‘Personalization across devices’ mean?
By better understanding how different browsers and devices are related, we can use information from one browser or device to help personalize the Twitter experience on another. For example, if you commonly use Twitter for Android around the same time and from the same network where you browse sports websites with embedded Tweets on a computer, we may infer that your Android device and laptop are related and later suggest sports-related Tweets and serve sports-related advertising on your Android device.
So, if I understand this correctly, all devices hanging from the same router at home will be understood to belong to the same person, since they share the same i.p. Therefore, if someone visits me and asks for the wifi password and that person does not have a twitter account, that person’s browsing will reflect on my twitter feed. If that person has, for example, particular sexual fetishes or looks for info on a desease he or she may have, I will suddenly get tweets on that subject. How great.