The text say that they infer that a device is associated to your account from your ip. They don’t need to infer that from your ip if you logged in and left a personalized cookie on that device.
The text clearly says that all unlogged devices from the same ip will normally be associated to the same person, which makes sense if they expect people to only use the app (on a phone, then) and want to follow them on the pc. I suppose that they would also not do that if there are multiple tweeter accounts in the same household.
I understand that other social networks do the same, but this was the official text from tweeter. I suspected that there was something of the kind, because the last time I visited my mother, I used her wifi and was surprised to see advertisements I was not used to.
I am pointing out that this is a privacy problem for anyone who gives access to friends on their home network.
