Option d: nobody outside of the Twitter TnS teams (including Paul Graham) has any idea of what Twitter is detecting as spam and what not, and thus can't actually judge how good a job is being done. First, we don't see the spam that was outright blocked, so we have no idea of what the false negative rate is. Second, I bet that this is not a binary block/allow decision, but there are all kinds of ways of reducing the e…
The most ironic part is that Twitter will show the spam/scams, but hide other replies, from real people, that Twitter thinks are mean.