Is there actually any information in this? What do they mean by believed to be vanished forever? According to the BBC new article  "private accounts and tweets that have been deleted will not be indexed by the site."
Historically Twitter have been pretty good about ensuring, in their licences at least, things like deleted tweets are deleted even from external archives. It's what makes compiling a database of tweets - even for research purposes - quite difficult.
However, on Twitter there is an extra wrinkle: neither the site nor the API allow you to go back more than 800 tweets for any view, whether it be "search results matching X" or "tweets that mention me" or "tweets posted by user Y" (the one exception being "your own tweets", where you can go back 3200).
This means that if you tweet a lot, it is impossible for another user to go back very far into your history. Even you may not be able to go back that far in your own history. As an example: if you send 20 tweets a day, your history will be inaccessible to you within 6 months, and inaccessible to other users within 6 weeks.
Given that this information is seemingly just gone--inaccessible, unable to be found from the user interface of any client, or Twitter's website, or searches on Twitter--while you and I know that they didn't delete it (in fact, Twitter even implies as much in their documentation somewhere: that the 800/3200 are only "temporary" limits), normal people are going to consider that data "vanished forever".
Remember: for a normal person, those somewhat scary-looking URLs are likely opaque. To the extent that people spend any time pulling them apart, it turns into a game of "guess the really long number, by hand, typing attempts into the URL bar of their web browser". They are unlikely even to figure out that it is monotonically increasing (which may or may not even help given the volume of the site); and, even if they did, for them the probability of guessing one of those numbers would still be effectively zero.
And we're supposed to take this seriously? Come on, doesn't it take more than a bunch of unsubstantiated claims for the HN community to jump on something and just take it at face value?
Still, not something I personally have an issue with, and I suspect not something most people would have an issue with.
What if you switched back and forth between private and public a bunch of times? Were those private tweets lost or did they reappear when you went public?
My gut says everything stays in the database and it's all being sold.
I agree, however: if you want to keep your thoughts private, don't post them on the Internet. When do you do that, they don't belong to you anymore.
"private accounts and tweets that have been deleted will not be indexed by the site"
Now we have all become artists; our words, our emails, our tweets and posts the new music. The Twitters and the Googles are the new record companies and once more the confusion between music and vinyl has arisen.
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