That article basically agrees with me. Additionally -- notice how it doesn't point to explicit existing examples, but implies "future problems" -- as did the 2006 article.

"In the vast majority of cases, cloud data that is accessible by the end-user will meet discovery needs and obligations."

and

(regarding going after cloud providers) "Serving a subpoena and ensuring compliance can be challenging and potentially expensive. Whether such efforts are worth the expense and effort will depend on the specific needs of each case. Cloud providers are likely to resist compliance with a subpoena under provisions of Title II of the Electronic Communications Privacy Act, otherwise known as the Stored Communications Act (“SCA”)."

Additionally, a director at http://tsemerge.com/ is hardly an unbiased reality oriented 3rd party. The more scared you are -- and the more complex it seems -- the more likely you are to hire them.