It does no such thing and proves neither. A ridiculous headline and a worthless article.

It seems to me that it proves Twitter's weakness, in the sense that Twitter ultimately must comply with the law, however unconscionable that law may be, but also Twitter's strength --- Twitter did fight the subpoena and may have done so successfully.

It doesn't seem that it proves Twitter's value, except in the sense that WikiLeaks is a savvy enough organization that it wouldn't be using Twitter unless it thought it was valuable enough to be worth the risk.