Like Bit.ly? Unfortunately, it might be going the way of Twitpic and the dinosaurs soon, if Twitter has anything to do with it.

Today officially marks the day that all links on Twitter which are greater than or equal to 20 characters will be automatically shortened using t.co, Twitter’s own URL shortener. And by automatic, we do mean automatic – you don’t have a say in this whatsoever.

If you’ve noticed your Twitter timeline filling up with t.co links over the weekend, you’re not alone. Twitter began rolling out this new feature a few days ago, with all users having access to it Monday.

The change basically means that all links greater than or equal to 20 characters will be wrapped in “t.co”. And this, unfortunately for us stats and analytics buffs, means that bit.ly is in trouble. Here’s Twitter’s official explanation from their developer blog:

“Beginning August 15th, when a user tweets or sends a direct message containing a URL 20 characters long or greater (the length of URLs wrapped with t.co), the URL will automatically be converted to a t.co-wrapped link. We will eventually wrap all links, regardless of length, but until then there’s nothing you need to do to support this change. When we’re ready to wrap all links, we’ll give you plenty of time and make another announcement.”

While a lot of people might think it’s just fantastic that Twitter has an official URL shortener now for everyone to use, the kicker is the 20 character limit and the fact that no one has a choice about using t.co or not.

Most URL shortners out there, including bit.ly, are at least 20 characters. So that means that if you use bit.ly to shorten a link and then tweet it out, it will actually be wrapped in a t.co link before being sent.

Joel West at Open IT Strategies did a little experimenting with this, and found that a pre-shortened link is now wrapped in t.co, but will appear like the original link if you view the tweet on Twitter.com – however if you hover over it, you’ll see a t.co URL instead of the original.

This is going to be a huge headache for companies like bit.ly and those of us using them for analytics. I’ve done a quick check, and many of my bit.ly links are now showing “t.co” as a referrer instead of Twitter.com, but Twitter.com is still appearing from time to time. Not only will this deter people from using bit.ly (after all, it’s just more convenient to shorten using t.co), but it is going to make things more complicated for those who do stick with it.

It’s no surprise why Twitter is shortening with t.co now, and not giving users a choice about it: they want to own link analytics. Of course, they’ve explained the move in such a way that it looks like it’s about security and the consumers, but the move really benefits Twitter more than its users. By wrapping everything in t.co, Twitter will be able to easily monitor link engagement (such as retweets and click), and will likely begin selling this link analytics data to big companies running Twitter campaigns. It’s a long-term monetization strategy.

This new announcement builds on Twitter’s move in June, which saw links pasted into the “What’s Happening” box at Twitter.com shortened using t.co if the user chose to, but kept the link intact visually for anyone viewing the link. Now, you just don’t have a choice about whether you shorten it or not.