The idea is floating around that Twitter will allow users to edit their tweets, possibly for a limited period of time. I agree with the desire for this feature, but it won’t work. Once a tweet is published, copies of it are delivered in real-time to thousands of data collection scripts capturing tweets with the streaming API. These copies are then put into thousands of databases, in some cases with the goal of permanent storage. It is impossible for Twitter to force changes to these stored copies of tweets once are delivered by the API.
This problem is apparent right now when tweets are deleted. Old copies remain all over the Web. In theory, the Twitter Terms of Service requires developers to remove deleted tweets from their own tweet storage. The streaming API even sends out a signal to alert developers of deleted tweets, so they can be removed. In practice, this issue is ignored, and deleted tweets remain permanently available at sites like Topsy.com.
Keeping track of changes due to editing tweets will be even more difficult. The edit may be allowed on Twitter.com, but then a mechanism must be added to the streaming API to notify all consumers of this stream that an edit has been made. Even if API users wanted to update their own databases to reflect the edits, pushing through these changes to an entire tweet collection system will require major rewrites. The contents of each tweet such as tags, @mentions and URLs are spread throughout complex data structures with the expectation that they are written once and never change. I see it as highly unlikely that these rewrites will be made. So unlikely that it just won’t happen as a general rule.
Twitter can try to allow edits to tweets, but the results will just be a mess, with multiple copies of each tweet popping up from different sources.