Twitter has just activated the retweet button a small number of accounts, according to a blog post. The new retweet functionality was originally announced back in August.

As we’ve written in the past, Twitter has been tweaking this new functionality for a while, making a pretty significant change to the API prior to launch. Previously, Twitter was requiring third party developers to check whether a tweet has already come in or not in any users’ stream to see if they should collapse it under the new retweet structure.

Now, Twitter has built its own mechanism to check for those duplicate tweets into the API. This will ensure that only the first tweet is shown and the retweets go under it automatically.

We’ve already previewed how the new retweets will look in one third-party app, the as-yet-unreleased Tweetie 2.1. This implementation looks pretty nice, and is not as cluttered as the one previewed by Twitter itself.

Previously, it was also stated that the retweet function will only gather up to 100 retweets, which is limiting.

Here’s the text from Twitter’s post today:

“We’ve just activated a feature called retweet on a very small percentage of accounts in order to see how it works in the wild. Retweet is a button that makes forwarding a particularly interesting tweet to all your followers very easy. In turn, we hope interesting, newsworthy, or even just plain funny information will spread quickly through the network making its way efficiently to the people who want or need to know.

You may remember that we shared the mechanics of this feature with developers a while back so they could think about how to work it into Twitter apps. Now we’re ready to start trying it on Twitter. The plan is to see how it goes first with this small release. If it needs more work, then we’ll know right away. If things look good, we’ll proceed with releasing the feature in stages eventually arriving at 100%.”