Unlike many posters here, I REALLY LIKE the t.co shortening idea. In addition to enabling the blocking of malicious links, it will enable Twitter to start offering some metrics and buzz rating on shared links. I might have an issue with adhering to the letter of the TOS, if not the actual spirit.
To get to the point, I need to introduce our platform....so let me explain our Twitter use at BuzzRadius (platform) and STL Tweets (canonical example). In each "metro" vertical silo, we consume a curated list of users (organised as per-category Twitter Lists against per-top-level-category twitter users -- e.g. http://twitter.com/STLT_Politics/city-of-st-louis) using the timelines, and ALSO consume a ton of searches for hashtags- per-category, a search against common local terms terms and the old- style (Summize based) search for geocoded profiles in a radius around the metro area. This gives us a local lens into Twitter that we offer up to anyone (even not using/having a Twitter account). You can see an example of the platform in use at http://stltweets.com Once we get tweets, we extract the RawLinks, Hashtags, Mentions and label/categorize them based on which of the sources provided the tweet. We then offer those categorized list of tweets under the various tabs like http://stltweets.com/Tweets/CityPolitics we provide a local search against the curated tweets (to enable focused results). The INTERESTING part is that we then take the RawLinks and canonicalize them and explore them to solve several problems: 1) We want the meta-data of the final destination of the Link... headline, body-text, media-type, etc. This allows presentation of "type-specific" link lists (e.g. Photos, Videos, Audio, Location, News, etc.) We can also grab thumbnail and embedding information to enable presentation on our side where possible. 2) We want to take all the RawLinks that point to the same actual destination link and follow them all the way down and associate the RawLink to a canonical Link. We do this by following links, redirections, frame-busting, query-string stripping of utm-tracking (etc.), link rel="canonical" and all that other fancy stuff to get a URL that is the final destination of the RawLink. This allows us to calculate a Buzz value for the Link based on how many people tweet about it, how recently, etc... EVEN IF the use different sources, shorteners, etc to get there. 3) We provide an ordered/ranked list of Links whenever a user visits a links page like http://stltweets.com/Links/CityPolitics if someone clicks on a link on this page, we send them to a Link detail page that show the meta-data and all the tweets that reference the Link (independant of the RawLink that leads there). 4) In the next deployment, we will also be doing ANONYMOUS link click- through tracking of the presented links to also gather the resonance in our audience for feed-forward into the Link ranking in bullet 3. Right now, that tracking is done only when clicking off the Link detail page like http://stltweets.com/Links/CityPolitics/Detail/804058 but we're also going to be redecorating the Tweet links when rendering the tweets in a stream. SO FINALLY TO THE POINT: In our current release, we present the RawLink in the tweet without redecoration so once Twitter starts feeding us t.co links, we'll be proffering those up just fine. Were good to go on any pages showing the original tweets (any Tweet list, including the list of tweets referencing a canonicalized Link). In future release, we will still be okay, because we'll click through our site and serve a 302 redirection to the "original" t.co URL (which in all likelihood is also to a shortener, but no matter). In our current release, when we show the user the canonicalized Link page, the tweet listing is good to go (see above), but the Link detail section at the top is NOT compliant because we cannot tell WHICH OF MANY possible RawLinks the user is "interested in", so we cannot serve the "original" link at all. Once Twitter starts serving t.co links, we cannot know which (of possibly many) the user is responding to. This sucks for Twitter, because they can't gather metrics, or mal-filter. In our case, we distribute the "clicked juice" to ALL the RawLinks that canonicalized to this Link based on the number of tweets that each RawLink got. It's an estimate, but it is all we have. In a future release, we will be putting in a best-effort change in that if a Link has only ONE RawLink referring to it, we'll actually click-through that RawLink instead of the canonicalized Link. This will enable proper tracking in a original URL (e.g. the utm-tracking, etc that we stripped will be honored). Once Twitter starts serving t.co URLs, we'll thus pass through per the TOS. As you can, however, we cannot ALWAYS do the right thing, because we don't know which RawLink to redirect through if the user clicks through the Link instead of the Tweet. So, who's going to yell at us?