[Autious]

It sounds like the user had removed the tweets from his account to hide them from public viewing. (I might be wrong here, not the point)

But, is there some law or other reason that Twitter would continue to store tweets that have been removed by its users?

[elarkin]

There very well may be a legal requirement. There is with email. If I understand right, a company must retain all communication for something crazy like 3 years.