Twitter.com has announced to end support for basic authorization by June 30, 2010. This means twitter clients and applications will not be allowed to access information using username and password of users. Developers have been asked to switch over to OAuth.

@raffi, the Twitter API engineer, has announced this update. He says:
Our plan is to turn off basic authorization on the API by June 30, 2010 — developers
will have to switch over to OAuth by that time. [ … ] Streaming API will still support basic auth.
The Twitter API team has also launched a website: CountdownToOAuth.com.
Migrating to OAuth will make twitter more safe. The users will not be asked for their account password, as OAuth method does not require such parameter. The Developers have already started migrating their application to OAuth. For example, the most popular image sharing tool, Twitpic.com, recently moved to OAuth from basic authentication.
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Twitter To Kill Basic Authorization, Developers Will Have To Opt OAuth [link to post] – on twitter