We criticize free services all the time for this, but I think that paying users are monetized all the same. Using American examples, the DMV sells data, internet providers are selling user data, credit card companies are selling user data... so it's not like any other companies don't monetize their users in other ways.
This is true. Paid services also tend to parasitise their legitimate users and maximise revenues.
A key difference is that in the Twitter case, there's no monetary penalty which can be imposed by the host class (that is, the unpaied content contributors).
Much of the "harvest as much data as possible" element is also driven by fundamental power and monopolistic differences.
