Another side effect of deletion is, that this single tweet is no more secret and may be too late. Hopefully it was not re-tweeted by someone before your deletion.

Another good reason for the duplicate re-tweet checking change on the Twitter API is to prevent spamming. Let’s say a new user is created and writes a script tweeting nerving stuff multiple times. This will be detected and disabled.

This way of clean up may also help to keep the database a bit smaller.