Nope, if someone clicks on one of my links on Twitter the referer field is empty. If I click on Facebook I get a Facebook url. That is a problem for both Twitter and web sites.
Reread it again :). Especially look at the charts.
Like the author, I personally see t.co in my server logs.
It would be pretty hard for Twitter to remove the referrer altogether (and I'm not sure what the point would be; they should want people to see that they got traffic from Twitter). Just did some research on ways to remove the referrer and found this: http://coding-talk.com/f14/how-to-remove-referral-8570/. At comment #8, they suggest making links via Flash, using https, or using a redirect (which is what t.co is). Users could also do it by configuring their browser to not send along the referrer when they make new requests, but Twitter wouldn't have control over that.)
